This is a good change, I think. Last month we arrived a little after 8:30 and my husband and son had to stand in line until 9 before they would allow sign-ups. Then there were about 10 people ahead of them so by the time we met up with them it was almost 9:30. We had planned on trying to do TSMM standby but by then the line was up to an hour wait. If they could've signed up for JTA right away, we could've gotten on line much sooner.
Unfortunately, I fear this will go the way of FastPass+ for parades and fireworks. The point is to show up right before the start time and still get a good seat, but people are showing up 1-1.5 hours early with a FastPass+ which defeats the purpose.
If the new plan is that JTA sign-ups start an hour before park opening, people are going to start showing up two hours early to lineup. It was a fun experience for my son and definitely adorable, but I'm not going to line up at 6 AM to do it again.