I will echo the comments made about that steerer. The join line and creases elsewhere look absolutely awful and hint at a potential deathtrap IMO. The hole for the integrated cables is at best a complete mess, at worst as above.
You shouldn't accept it or ride it IMO.
Generally TopCarbon have a decent(ish) reputation but that never should have made it to completion on the production line, let alone QC, let alone been sold to a brand / retailer, let alone been sold to a paying customer.
The workmanship is appalling.
It seems like there are much bigger things to worry about than poorly chased BB threads (on the Riot) with TopCarbon, or at least the stuff that gets sold as Lexon.