This may apply to someone characters in general.
The English translation of the databook said that Ichigo was fast like-lightning. [1]
It was not accepted for been unquantifiable. I understand that much.
But that was an error translation.
The raw Japanese databook says, "that Ichigo is fast as lightning" [2]
Which means Ichigo is Mach 289 in SS Arc onwards. Lieutenants maybe Mach 29 according to the previous calc, but not captains as shown by most of the elders that never train affer the timeskip, but that is another discussion for another thread all together.
Gin Mach 500 debunks this? No.
Even if Gin didn't lie to Ichigo about his Bankai speed, it was still Mach 500. Ichigo couldn't had match him with Mach 289 as low-ball. <ac_metadata title="Bleach Speed Revision-Pre-TimeSkip" related_topics="Bleach|Ichigo Kurosaki|Byakuya Kuchiki"> </ac_metadata>