IMO the auto branch would still flower separately from the photoperiod host plant. I have a… crafty fruit tree, it’s a normal root stock but was grafted onto with 6 types of fruit, although they all share the same host, each brach acts independently, AKA the plum branch may fruit this year but the apple beaches will mature for another year.
The biggest problem with the method on photo with a grafted auto branch will be if both need the same neut requirements at the same time, if you can get the auto brach to take to the new host without over stressing it
Would still be cool to try to see how it would respond though