Something I find a little interesting is that Goku and Vegeta clearly don't recognise Freeza's transformation with them even asking how Freeza killed Gas when it seems like Freeza did transform into Black when killing Gas. Notably Goku was in TUI when that happened, and UI gives the user vastly superior agility so his own perception should be significantly superior to Vegeta.
That does tie into Vegeta recently mentioning Explosive Power from Jiren and tying it into characters like Freeza but the thing is that Jiren's version only let him match UI Goku's movements whereas Freeza can seemingly transform and revert so insanely fast that not even TUI Goku can perceive it happening or understand how Freeza could have even done it in the first place. Meaning Freeza's power control is so advanced that his power is truly unreadable to even a UI-user.
You could argue that's just Black Freeza's raw speed in the actual attack but my point is that Freeza had to go from Base -> Black -> Base in such a ridiculously short burst that not even Ultra Instinct is capable of perceiving the power changes, and if the colors are accurate then Freeza's aura doesn't even change and he's already reverting the moment his arm is through Gas's chest.
There is also the point that Goku has a hardening ability via UI yet Black Freeza deals the same amount of damage to him as Vegeta. That could be plot convenience, Vegeta being more durable, Freeza just having that level of control punching at the same time or Freeza being so fast that Goku couldn't even harden his body in time.
So, Freeza can go 0 to 100 to 0 so fast that even TUI Goku (Who has Analytical Prediction, enhanced agility, Instinctive Action, resistance to Information Analysis) can't even perceive it and possibly so fast physically that Goku can't act in time to harden.