Seems a bit odd as a general question, but...
But a valid concern, ne're the less, given some bloopers made by manufacturers! However, the question of being "correct to scale" is not actually wholly separable from questions of dimensional and other accuracy...
It is, I think, really a kit-by-kit evaluation. Probably, as stated by others, no kit maker actually really flubs the scale across its line-up - but many - maybe all - flub one or another kit in awesome ways. Consider the gross dimensional/proportion and size issues which have emerged around the recent RSO kits produced by Dragon (you know - the Big D; Big maker, very well-known, hugely respected, often touted as the general industry "standard-setter" for many years...). One can interpret the wrongly-proportioned RSO as being either the "wrong size for the scale" (The cargo bed is, for example, perhaps only 80% as wide as it should be... so it could be perhaps a 1/48 RSO bed, in width!) or "it's the right size for the scale (the RSO bed is, I believe, long enough to be a 1/35 scale bed), but way off in proportion" (thus, way too narrow, a fundamental "proportional accuracy question"). D blew that RSO. But this should not, I think, call into question much about the rest of D's huge line-up. Each kit has its own ups and downs.
Bob
