Yes, you're right. The animation isn't glitchy, they literally re-worked the animation to be exactly how it's being shown.
Apple did this because they want the animation to start immediately on the first click, rather than waiting for a second click before returning home.
It's like this (for anyone that's interested)
iPhone 6s:
1. User clicks home button once
2. iPhone says to itself "Don't do anything yet! We don't know if the user is going to double click, so we don't know what action to take just yet!
3. After a second or so, the iPhone goes "False alarm! User just wanted to go home! Start the home animation!!"
4. The screen smoothly transforms into the size of its home screen icon.
iPhone 7 does things differently:
1. User clicks home button once
2. iPhone says to itself "Start the animation! We'll deal with a second click as it comes!"
3. The wallpaper however, cannot move yet because the iPhone doesn't know when you'll do the second click.
4. If a second click is detected during the initial animation, the iPhone says "Wait! The user clicked again! Interrupt the current animation and show them the multitasking screen!"
Because of the fact that the iPhone has to be prepared to show the multitasking screen, the way the app animates to the home screen is different. It starts off by shrinking the screen slowly, but keeping the same proportions of the app screen (16:9). Once it gets past the size of the multitasking window size, it starts to distort slightly and blend into it's icon on the home screen. However, since the zoom animation started off slow, it has to make up time by speeding up toward the end of the animation, but someone forgot to tell the wallpaper that, so it lags behind the rest of the animation.
That's why the iPhone 7's animation looks off-putting.
If they could just get the wallpaper to move at the same speed as the zoom animation, it wouldn't look so weird or delayed.
I hope this helped some people out
