Even by Toyo's standards, I don't think he'd be so asinine as to believe that was enough for Vegeta to become vastly stronger in general, not to mention he and Galu are presented as on par in SSB even after the Rosat training.
If anything, Vegeta training with Trunks strengthens the idea Vegeta increased the Ki output of SS2 when he'd just seen Trunks do the same to match SS3's amp.