Question about global skills + undo in shop

Is using the 'undo' in shop an advantage for champions with global skills?

3 scenarios I can think of is :

Say, Ashe has ult and gold around 1600. She can buy the rod for + AP which is beneficial for her ult then exchange for BFSword/Zeal and Boots.

Another is Kart, where he can cast his ult with the rod, then undo after, and go with chalice of harmony + boots.

Last is Soraka, which badly needs her ult, goes for CDR boots, casts ult, undo then go for mobility.