Unnecessarily aggressive and arrogant post, particularly given you are completely wrong about there being no chance of them being genuine (even if I agree with the rest of your post about their business practices).
Shein do primarily sell cheap stuff but they also sell branded items. If you look on there it's a bit of a disconnect because the majority of the, say, trainers are £8-13 but then the branded items are £80-100 -i.e. not particularly cheap, probably the same as youd get from sports direct. There are also far fewer of them than their unbranded options - e.g. only certain sizes or whatever.
although they do absolutely rip off designs etc if youve ever actually been on there youll see they are very careful to use vague descriptions and never useaor refer to a brand name unless it is the genuine item- they are such a huge site I presume they are very aware they'll be checked and sued if they try to pass off counterfeit goods.
I presume they probably get job lots of last season trainers or the trainers are made in the same factory as their other stuff or there is something very slightly wrong with them or whatever which is why they sell them. Or use them to draw in people like OP who just Google for the brand name and who wouldn't otherwise be sheins target audience.
They also have a fairly generous return policy so it would be pointless selling obvious fakes because the buyer would just return them anyway.
Either way I'd be very doubtful if they weren't genuine - not because I have any delusions about sheins morality but because they'll be protecting their own interests.