I think it's a waste of time having him fight 6' ish heavies to 'test the division' because most of these guys are just blown up cruisers or literally fat cruisers (even fat LH). They are probably not functionally bigger than cruisers and possibly far less skilled than top cruisers. Usyk should have little trouble with these, you'd think the problem would be how does he do against the 'super heavies'. So they should put him in with the 6'5 ish heavies. Put him in with Helenius or someone like that. Then he'll get a better gauge. Seemed to do well against Joyce. If his goal is heavyweight glory, he has to get through the giants.
I think they were talking about Povetkin, initially as his first HW fight, but that's now been delayed as Povetkin wanted a tune up. If Usyk beats Takam and then signs to face Povetkin he won't be taking on one of the giants of the division in physical terms but in every other way he'll be facing one of the best that there is. Whether either of those fights are sufficient preparation for a 6.5+ giant is another question.