I have some Verbatim 5 Color Collection discs which are sold in 25pcs. The discs are stacked right up to the top and there is a really thick spacer at the bottom. I am quite sure the cake box without the spacer should fit at least 30 discs. And yes, these are real TYs. They have the prerequisite TY stamper code GG/GD/TC/TGxxxxxx.
The cakebox used by the Verbatims looks to be the same as the ones for Panasonic. I have actually seen those Pansonic discs on sale and handled a cake box of it.
Btw, I have seen Panasonic disc in a 10pc TY cake box so there actually are 10pc TY cake boxes.
As stated, those are real TY discs but that doesn't mean they cannot sell fake TY discs alongside real ones.