The differences between this and the D20 "Tiny Hut" are informative: http://www.d20srd.org/srd/spells/tinyHut.htm
The D20 version explicitly states "However, if you remove yourself from the hut, the spell ends." - 5E's wording is far less clear, but I would interpret it to mean the same thing: being able to see the evolution of the spell description in this way makes the intent of the designers obvious, even when their words are less than clear in the final product.
This is also useful for tackling the question of what happens when the ground isn't perfectly flat, or if the caster is casting it at the top of a pillar, or upstairs in an inn: the D20 rules explicitly state that it's a sphere, but only a dome is normally visible, which makes intellectual sense. This also precludes abuse by casting it on a cart, for example, as the buried part could not move through the earth.
This "see how the spell evolved over time" idea obviously can't be applied universally, though: the 5E rules must still be considered canon, in a 5E campaign, and all the D20 rules can do is give a suggestion at what the intent of the designers might have been, in grey areas like this.
For example, the D20 version is far less exploitable by savvy players: it is not invincible against incursion by foes or magic: it merely provides cover and shelter, and can be destroyed if trampled by a mob. Personally, I feel this is in the spirit of the spell, as being intended to provide a simple tent like level of protection, rather than an invincible shield/gun-turret/lava-cooling-device/etc. But whatever my feelings, the 5E rules are the rules: which means, the GM needs to handle the fact that the players have the potential for an invulnerable 20ft dome of invulnerability at low level, and if cast as a rune, they can even erect it instantly: http://www.enworld.org/forum/showthread.php?358657