From my testing it appears like the period is being ignored altogether. When I request all videos I get the complete list every time. I guess this is both a good and a bad thing.
It’s good because I was actually able to request all videos. That means they finally fixed the cursor offset bug that prevented you from using a cursor that resolved to an offset of 600 or more. Well, sort of. For some reason I can request all videos when I try and only filter by period but not only by type, sort, or language. But when I request all pages without any filters it works fine. The bad is obviously this endpoint is a mess and it’s nearly entirely broken.
My guess is they’re still in the middle of fixing pagination and caused some bad side effects since filtering worked well-enough before (there were still cases where filtering was broken, but not nearly as bad as it is now). Hopefully everything will be in working order soon.