Not quite.
As noted, deckplans for CT, MT, T20, and MGT are gridded at 1.5 meters, and thus at two floor grid squares per displacement ton.
The Classic Traveller designs in Traders & Gunboats vary all over the place, but two hulls are pretty close, and a third isn't too bad.
The Scout/Courier hull is actually pretty close taken as a whole. You do have to take into account the actual hull shape and what that means for the deck heights, as not all the depicted areas are full or even half height.
The other hull that is fairly close is the Subsidized Merchant. In this case, the oft-forgotten detail is that the cargo deck is double-high, while the wings are half- or quarter-high once you get out past the depicted engine sections.
The Close Escort seems odd, but is actually fairly close as these things go.
Most of the subcraft aren't bad either. The one exception is the Shuttle, which somehow got saddled with plans the size of the Pinnace.
The Marava, on the other hand, is way out-scale. The deckplans come in at over twice the design volume. The easiest fix (which also applies to the Beowulf from the much later Starship Operator's Manual) is to call the grid 1.0m instead of 1.5m. This has the effect of making FOUR grid squares a ton, and brings the total volume down within range. It does make the external view of the ship rather more squat than usually depicted, however.
The other solution is to do a statblock to match the plans, and completely re-do the A2 plans.
The X-Boat is close, but really, who cares?
The X-Boat Tender, on the other hand, is about 50% too large. No easy fix except to shorten the bay, and that sort of defeats the purpose of the design.
The SDB *might* be close, but with the plans being so chopped up, it's impossible to tell.
The Lab Ship is another case of "might be close", but as one of the oddest hulls in the Traveller setting, I'm not sure many people care.
The Type K from Adventure 10 "Safari Ship" isn't hideously out-size (though it is a bit bloated due to airframe considerations), and is coincidentally the best fill-in for the Type Y published to date.
The Type M from Adventure 13 "Signal GK" certainly feels fairly close to its 600 tons, but has some design oddities that make you go hmmm.
The various licensees who produced Classic Traveller products didn't do much better.
Somewhat amusingly, one of the cheapest actually got the closest. Judges Guild's "Starships & Spacecraft" contains quite passable Type A and Type R plans, and a decent set of Type S plans. Most of the other ships are also close, but *really* ugly.
FASA was worse than GDW when it came to deckplan accuracy. In about two dozen designs, they only got a couple very close. Their Alexandria Type A is probably the best set of Type A plans out there, and the Chatl Zhodani Leader Scout is surprisingly close to its 150 dton stats. Most of the rest are either badly sized or missing important details. Like fuel.