Core 2022 added:
Sensor Station (1 ton)
Laboratories x2 (8 ton)
Staterooms x5 (20 ton)
Common Areas (5 ton)
Cargo (11 ton)
... but forgot to make room for those 45 tons, so the version in the new book is "overweight".
As of why I didn't think it was supposed to be a full hangar: I was thinking of the deck plans in Gurps Traveller: First In and Grand Survey from DGP (that last one is where the Donosev first appeared, if I remember right). Oh, and it's in Mongoose Traveller v1 Compendium 3 as well (and probably other places).
In those deck plans, and the front and side views, the modular cutter is only partially enclosed inside the hull, which makes it unlikely it's a Full Hangar.
For some reason, the MgT2 deck plans are changed from all the previous ones (which are all pretty similar), though the stats and the outside still resemble the original design.
The older plans (and stats) do have 10 or 11 staterooms, 15 to 30 tons of cargo, often some armour, and (depending on the version) at least one and in other cases more than one laboratory, and plenty of common areas (lounge, galley, etc).
Also, having a Full Hangar (instead of a Docking Space) pushes the tonnage up to 445 (with a Docking Space, it is 400 dTons).