[Bikkuri]

"Are you sure about that?
Can not a toothpaste tube pop off a cap if squeezed when outside pressures are equal ?"

Think about that.. you have to squeeze the tube (implode) before the cap is forced off.
If you never squeezed the tube, the cap won't move (unless it was mailed USPS /s).

[A strike]

Might it not be likely for one component to squeeze more or earlier than another ?
Think about that

[cymbeline]

“you have to squeeze the tube (implode)”

Squeezing a toothpaste tube won’t implode it because the toothpaste inside is not a compressible material.