Exactly. The thing is that in some documents it says "the king" and not the monarch. Which doesn't matter much right now. But if there was a King Consort that wanted to take of advantage of that it could get really nasty. So they would have to change documents (which usually is a rather long process). So it's just easier to keep it as it is for the moment.
The Swedish Instrument of Government says that the person who is King or Queen according to the Act of Succession is the Head of State and, then, uses "Head of State" throughout the rest of the document, instead of King or monarch. The constitution of New Zealand, as I explained before, uses the term Sovereign and defines Sovereign to be the same person who is entitled to occupy the UK throne under the Act of Settlement (as amended, e.g. in NZ, by the Royal Succession Act 2013).
In other words, there are many ways to avoid any legal confusion between the King Consort and a Sovereign King, Out of respect for tradition, I agree though that the best solution is simply to call all royal consorts prince or princess with the style HRH. That will be the case with Camilla in the UK and, hopefully, it will set a precedent for future would-be "queens" by marriage.