Oh, I get it now. You're not having a conversation with me. I was wondering. I've stumbled into some pet peeve of yours and now you are busy engaging in some tired old but still heated debate you've had before.
A design is incoherent if the design direction from one set of rules works against some other element of the design. To give a hypothetical, suppose a homebrew version of D&D increased all the hit points of all characters by a factor of 10, but then at the same time an additional house rule was introduced so that whenever a character took hit point damage the character had to make a fortitude save with a DC equal to the damage taken or die. These two rules end up working against each other. The increased hit points now almost never matter, because the ever present risk of death after every wound will dominate concerns of play.
I maintain that the text of Planeshift is poorly thought out and has inadvertently introduced the same sort of incoherence where it is working against it's own design.
The way the spell worked in 1e, 2e, and 3e is introduced not as evidence that the spell is objectively incoherent, which as I said need only depend on an internal comparison, but that the change was an unforced error brought about by a writer who wrote the spell prior to (and without playtesting) and not in response to the needs of the game. The comparison remains valid (since the problem doesn't exist in earlier editions). At best the new version trades one convenience in scenario design for an annoyance in another. It seems entirely possible to create a version of the spell for 5e that had the convenience by not the annoyance.
Comparison between two things in a rule set is an entirely valid perspective, and my strong suspicion is that outside the context of this argument you would accept it as common sense and entirely realize it's importance. As a hypothetical, imagine a home brew class was introduced for play and it was strictly superior not only to an existing class, but several existing classes. It would be entirely fair to compare the new strictly superior class to existing classes and say, "This is massively more powerful than existing options, and entirely deprecates several classes. I don't think it would be helpful to the game to introduce this class as written."
No, I don't appear to presume that at all. This is you engaged in whatever argument you are resurrecting from your past.
Ok, yeah, I'm beginning to get the gist of which pet peeves you are importing to this discussion.