The Speed of Biju Bombs
Consequently to the previous threads, the speed of the
Juubi's own Biju Bombs - being significantly more powerful than Gyuki's Biju Bombs - would also be faster than light, and yet there are scenes that would strongly indicate against that assumption.
In Chapter 613, the Juubi undergoes its evolution into its second form and
begins spammning long-range Biju Bombs to rain down in distant locations. The last of these is aimed for the Allied Shinobi Forces' Headquarters located in the vicinity of Kumogakure. We then get an extensive sequence where
the sensory shinobi realize the target of the Biju Bomb, relay it to the others, they discuss the situation and then Shikaku has the telepathic ninja relay his plan to beat the Juubi to everyone on the battlefield before the Biju Bomb lands. We can then see the explosion in the distance and Madara remarking "
Finally got them."
For reference, the area where the Juubi is - where the alliance is fighting it - is indicated by the red arrow. The Allied Shinobi Forces' Headquarters is highlighted by a purple arrow.
Our
currently accepted value approximating that distance is around
700 kilometers, and even with other methods it is
at-most around a couple thousand kilometers.
Remember that lightspeed means
a projectile could circle the Earth approximately 7.5 times in one second.
But here we have multiple characters conversing each other, being shown in contemplation, coming up with ideas... and then to end it off, Madara remarks that they 'finally' got them after waiting for the Biju Bomb to land. This is not the kind of remark one would make if he was just waiting for a hundredth of a second. There is significant travel time for that amount of distance.
While it's a common convention that "Talking is a Free Action" and characters can execute high-speed maneuvers while still speaking normally, this goes well beyond just a line or two. These are full-blown conversations that don't make any sense if an FTL projectile is crossing so short a distance.
The much stronger Juubi's Biju Bomb being this slow should call into question Gyuki's Biju Bomb being assumed to be so fast.
Mifune's Issen
There is room for doubt as to whether or not Mifune's technique itself is a lightspeed projectile. The only basis for Mifune's technique being as fast as it is comes not from the manga itself, from a secondary source,
the databook, which is only applied for the Naruto-verse on a case-by-case basis due to some discrepancies and hyperbolic statements such as
Sasuke's power exceeding even that of the Akatsuki.
This has been translated by @Arc7Kuroi as:
What the statement in the databook is saying is that Mifune (who uses Iaido, a high-speed form of swordsmanship that is about drawing one's blade quickly and slashing), is slashing his sword at lightspeed and and releasing a flying slash at his enemy.
Even if we took the statement literally and assumed there was no databook hyperbole going on here, we could say that Mifune's sword stroke was executed at the speed of light, but the projectile sword-slash that is released by him is not necessarily travelling the quickly. The databook makes no actual mention of Mifune's flying slash being what is lightspeed.
Although Mifune's technique Issen, can be translated as
Flash, or
Beam of Light, this again doesn't mean the projectile has to be lightspeed. It's not a literal beam of light he's releasing, but a projectile of chakra released from his sword-swing.
Same as all the other regular samurai who coat their blades in chakra and release slashes of chakra that Sasuke is able to react extremely casually to.
Not to mention that describing someone's attack as a "speed of light sword stroke" can easily be a figurative description rather than an absolutely literal measurement of their speed. It conveys the meaning that Mifune's attack is fast which is all that matters.
Assuming we disregard all that though and still insist that it is Mifune's flying slash that is lightspeed, the original argument depends on the assumption that all of the attacks were launched at the exact
same time. There is no chance that the shinobi and Gyuki were able to coordinate their moves that precisely; even a microsecond of time between the different jutsu starting to move would be relevant when we're talking about matters of lightspeed. It seems far more likely to me that Kishimoto just wanted a scene of several characters through ranged attacks together and didn't put any serious thought into it of them all having to be
exactly the same speed, and that the minimum speed they'd need to travel is lightspeed.