You are right sir but this has one huge logically error. This would imply Beerus actually knows Goku...a guy he just met. He had no reason to assume that Goku is a brainless monkey.
Secondly he tried to keep his lie belieaveable even after knowing how dumb Goku is.
Again, show Beerus used actually just 10x more power with Goku that what he used against Vegeta.
His lies are, like that, just lies someone can easily catch if it's intelligent enough, he using a common mortal, not a barely strong one, not an actor able to show his strength with his words, but a barely common mortal with no merits to represent someone near the level of Goku shows that.
Unless you can prove explicitely, and not with such absurds percentages followed by headcanon, that Beerus used 10 times more power against Goku than what he used against Vegeta, Vegeta's nowhere near 3-A.
If you are pulling the " You can't use things that are not accepted" -card instead of arguments to win the debate , I am going to retaliate the same way.
Again: don't compare. You are just inflating Vegeta's growth to show it being greater than Saitama's, with headcanon and no actual proof more than "But Beerus said he used 100% against Goku and just 10% against Vegeta, he wouldn't make it incoherent for a lie, right?", which is more a headcanon than an actual and factual thing, unlike Saitama's growth.
Also the reason why things needs to be discussed in a CRT befoe being accepted is because a) they can be outlier
do you know what an outlier is? If you know, you should already know that argue something about a character whose full strength was completely unknown and that is directly the god tier of his verse is an outlier is dumb.
b) circumstances need to considered( like his growth rate being rather flat before jumping due to emotion amp)
"Saitama was constantly growing", "no one noticed it because no one forced him to be 100% so far", "because of his emotions, his growing started to soar". Instead of explaining the process of accepting an ability, something I already know, show how Saitama's growth is contradicted or an outlier, as you want to call it.