Untrue. The cartoon explained all the ones that started the series as being rebuilt from their Cybertronian forms and later characters with Earth forms were either built on Earth or introduced with no backstory on Earth.
In the One True Continuity (i.e. the Marvel UK comic run of the 1980s), the Earthern forms of the Transformers were by and large something that were always explained when they left Cybertron; those Transformers not created on Earth generally (but not always) had their alt-modes surgically altered (because it wasn't something they could do on the fly as in later continuties, e.g. the movies) to Earth-compatible ones (often off-screen), and whenever you saw them in pre-series flashbacks - or before they'd come to Earth - their vehicle modes were 100% Cybertronian (though, granted, close to the character's Earth (i.e. toy!) form so as to recognisable, for obvious reasons.)
Spoiler
Pictured, Cybertronian vehicle modes of Seaspray, Poweglide (with Blaster dangling beneath, Beachcomber, Cosmos and Warpath, just prior to them arriving on Earth in the 1980s (they hadn't been on the Ark when left four million years ago, and ended up on Earth due to a battle for the Decepticon Space Bridge.)
Not really, not in the beginning. The "robots in disguise" tagline was more a Thing for the toy line at the time, than of the G1 continuity itself, especially in the comics. More recently, with stuff like IDW, more was made of it, but not really in G1, in either cartoon or comic.Originally Posted by Gamer Girl
In the comic, the "disguise" thing wasn't really very important at all, and usually the only time Transformers didn't recognise each other was when they actually hadn't met before. After that, they pretty much recognised each other in whatever form, because they weren't, y'know stupid. (Not even Grimlock and the Dinobots. Well, maybe Sludge...)
And the whole "transforming" thing was actually not over-emphasised. It was just something their race did, it wasn't their central focus. It was almost incidental (more so in the comics than the cartoon. Indeed, in the former, several major characters hardly ever transformed at all, e.g. Ratbat, Ultra Magnus, Thunderwing, who were only saw out if his pretender shell once.) It was about the characters and the war and not about the spectacle of transforming robots - and that was why, in my opinion, it still is the best continuity. (And why I find the Japanese continuation of G1 and later animation series unwatchable since it became so much more stilted and over-emphasised.) It is better, I think, when it's about the characters (who happen to be robots that transform) and the war they're fighting rather than being about Robots The Transform (and the war they happen to be fighting).
Not to mention as time when on, the increasing large number of transformers with flat-out undisguised alt-modes (Dinobots, Predacons, the Headmasters and their ilk that came from Cybertron, with Cybertronian alt forms.) Towards the end, neither side was bothering with subtle, generally. (E.g. the Underbase Saga!)
Those transformers - mostly Autobots and mostly with ground-based vehicle forms, as the fliers and beast-forms of both sides tended to be armed somehow - that didn't have weapons tended not to fight in vehicle mode anyway and only used them for transit (as Trailbreaker once noted in the G1 cartoon, one of the major reasons was "it beat walking..."), or hiding from humans who didn't know better (until they would blow their cover by transforming and fighting of course! Mind you, it should be pointed out that in the comics, this was the Marvel U, so the intelligent and perception of the local populace was pretty low...!) Heck, aside from the beast/animal formed ones, even the ones with armed vehicle modes tended to spend more time fighting in robot mode anyway. Even in the cartoon.Originally Posted by Gamer Girl