What happens when Restrained creatures are removed from the area of effect of Entangle?

The victims of an Entangle spell are Restrained and cannot move themselves; but can be moved by others. I had always assumed that moving them out of the Area of Effect of the spell would free them; but a close reading of the spell now has me questioning this.

Grasping weeds and vines sprout from the ground in a 20-foot square starting from a point within range…A creature in the area when you cast the spell must succeed on a Strength saving throw or be restrained by the entangling plants until the spell ends. A creature restrained by the plants can use its action to make a Strength check against your spell save DC. On a success, it frees itself.

As written, there are only two things which explicitly end the restrained condition; the end of the spell and a successful strength check by the victim.

Contrast this with the Web spell.

On a failed save, the creature is restrained as long as it remains in the webs or until it breaks free.

There, a creature that leaves "the webs" (=VoE?) is explicitly free of restraint.

However, note that with Entangle, the "entangling plants" themselves are limited to the initial 20 foot square (not cube), and while there they "sprout from the ground". Under the 5e principle that there is no flavor text in spells, it could be that the vines can only Restrain one while they are connected to the ground, and leaving the area does not take the plants along.

Note that if the vines wrap around anything, it is only the feet and legs – a Restrained character cannot move themselves, but they can still attack and cast spells. Restrained does not mean Incapacitated.

So, do these plant restraints remain tightly coiled around one’s legs, keeping one restrained even if moved away from the original ground, or do the restraints fall away once the plants are ripped from the ground?

Related: If you are pushed out of Evard's black tentacles while restrained, are you still restrained?