you said it yourself that god takes goku from 4B to 2C
so why isn't that just treated as it is for the multiplier
"reasonable lowball" is also kinda weird since god goku is literally magnitudes of infinity stronger than vegito, base vegito is significantly above the likes of Super Saiyan 3 Goku, and Super Saiyan 3 on this wiki is treated as more than 400 times since the Super Saiyan Grades, all of which boost power, are outclassed by Super Saiyan 2, which doubles Grade 4
The only reason why Toei has infinite speed is likely from a narrative mistake from Goku and Pikkon traveling across Otherworld and the authors forgetting that Otherworld is infinite in size, making it barely a feat and moreso a "the authors forgot about this but since it's technically a feat we will consider this anyways" kinda situation. No other infinite speed feat exists outside of DB heroes, which is why DB Super doesn't have any.
With this in mind, why is infinite speed still unreasonable to assume since the Super Saiyan God multiplier has a beyond infinite multiplier
I mean, ki is treated as an omniboost in every other aspect of the series with every other transformation, amp, and otherwise.
Heck, this wiki still tries to make Super Saiyan God a consistent omniboost by nerfing the transformation to be a x160,000 boost in EVERY stat including speed
so why would Super Saiyan God be ANY evidence of AP/power not increasing proportionally when everything else IS, and it itself is also treated as proportionally on this wiki due to the nerfed multiplier