To be CLEAR, this is not the same issue I've seen reported before (at least when I searched) so don't dismiss it as another "Bundles inside of bundles" bug.
You can use bundles to stack empty bundles.
To Reproduce this issue:
Have a chest full of junk items (dosn't matter what) and several empty bundle bags in your inventory
Be in survival mode
Place any number (up to 16) of your bundle bags into a bundle
Fill the rest of your inventory and hot bar with junk items such that there are no empty slots
Right click to open the bundle holding the other bundles which will now be disgorged on the ground due to a lack of space
You can now pick up the dropped bundles as a stack of empty bundle
See Attached image with a stack of 7 empty bundles in inventory
At this point, it can be safely assumed that putting bundles in bundles is not intended. Resolving as dupe of MC-203567.