I... am going to go ahead and extend MD 546, favoring consistency within the same state. Even though I don't really like this.
Maybe instead adopt a Utah-like and/or signage-based approach statewide?
I like that less than having MD 546 be inconsistent with what's done in Utah.
Within Utah, there is only the very specific circumstance that when the logical endpoint of a route is at a freeway interchange, often state maintenance will extend a block or two beyond in order to cover the approach to the interchange from the far side, ending where the project limits from when the interchange was constructed were. In these specific conditions, it causes little indigestion to ignore the dangling end; the route can be said to end at the interchange
in some sense.
Maryland is messier - MD 546 is the only one of the examples just named that is comparable to what's in Utah. 197, 367, and 610 are sections of plain road extending variable distances past the route's logical endpoint, whose inclusion cannot be explained by "well this is where the limits of a past project to construct an interchange were". So there the ball isn't close enough to the cup to take a gimme on it, the extension of the route has to be taken seriously as an independent segment of the state highway system.
I'm kind of just resigning to the fact here that I could spend all night overthinking this, but ultimately things are going to be imperfect in some way and that's not really avoidable. After all, route clinching is an attempt to make a game out of something its designers never intended to be a game. It is thus inherently full of inconsistencies and subjectivities. We just do the best we can to smooth them out.