Building boards generally, I feel, should be used on certain constructions of models. If we look at Companies such as Billings, the building techniques are generally well thought out and they rely on, shall we say, on the materials being used i.e. no warps or distortion in the plywood - to keep things true.
If you look at this particular build, you will see that it is the actual deck and the keel of the model which is creating a stable building platform. The thing is, when you actually come to plank this model, you are relying on some way of holding it while you are planking it to prevent it slipping/moving all over the place.
Billings, I believe, actually manufacture a jig for holding models, at a cost of course.
The reason I particularly endorse using a building board is, it not only holds the model securely and gives you a good working area - as previously said it prevents any distortion.
When I built HMS Warspite - years ago - it was at 1:96 scale, giving a length of something like 80 inches and I built this naively and without a building board / any forms of keeping it true. It twisted! I thought I would be able to pull the twists out when I added the anti torpedo blisters either side of the hull. Needless to say, it didn't work, the hull became a glorified plant pot - from then on I always use a building board - even when I built HMS Exeter at 1:96 scale and especially when I built the modern version of HMS York also at 1:96 scale.
The other good reason for using a building board, is sometimes we build hulls, where the framework is rather flimsy, until we get the hull planking skin on. When I built the Seaforth, she has a large moonpool in the hull - this actually cuts through the keel of the model, so we need to support this area whilst building.
Therefore, the building board use really depends on the type of model and also the construction method.
I have added a couple of photographs showing the moonpool - you will see one is of the hull upside down and where I am opening up the hole for the moonpool, after planking.
The other photograph shows the hatch open on top of the superstructure and this is the other open end of the moonpool so, literally, the moonpool goes right the way through the hull and even through the superstructure.
Guess what, I like using a building board 😊