Quote block still exists after deleting from post via backspacing

[hypest]

Describe the bug
After deleting a quote block and exiting the editor (or switching to HTML view) the quote block seems to still be there when opening the post again.

I've verified it both on WPAndroid, WPiOS, as well as the demo app.

To Reproduce
Steps to reproduce the behavior:

1. Go to the demo app or WPAndroid (tested on v18.4-rc-3)
2. Insert a new Quote block
3. Focus the Quote block and delete it by backspacing. Notice the block being removed.
4. Exit the editor (save the draft if asked) or switch to HTML View
5. Re-enter the editor and notice the quote block still being there, or notice the blockquote markup if you switched to HTML view 💥

Expected behavior
The quote block should not have appeared after re-opening the post, nor be there in HTML view after been backspaced.

Screenshots

quote_cannot_delete.mp4

Smartphone (please complete the following information):

• Device: Pixel 2XL
• OS: Android 11
• Version WPAndroid v18.4-rc-3, gutenberg-mobile develop 3f19075

Additional context
Add any other context about the problem here.

[hypest]

Marking this as [Pri] High as it involves a content fault.

[fluiddot]

I noticed that this can be reproduced with any block if it's added as the first item of the block list. After checking older versions, I confirm this began to happen in version 1.61.0 (18.2).

[fluiddot]

As mentioned in this comment, this looks like a breakage from a change in Gutenberg.

[hypest]

I'll go ahead and close this ticket for now and we can reopen if for any reason it turns out to only happen on native mobile.