If discussing 1:100 there is no individual attention, so why not 1:1,000 or 1:100,000 or just YouTube videos one can watch at their own pace.
In my college lectures of 1:200, there were still separate sessions of 20 students or fewer, led by grad students working for the professor, to offer more individualized help. If that doesn't happen and it's just a lecturer talking to a crowd, the ratio is irrelevant.