I've heard about alpha, delta, & whatever platforms & wandered who made them? Not sure, but thought the companies that produce cars as in Holden (past) bmw ford toyota, & whoever else.
Started noticing a resemblance between the different makes, as in the shells. Change the rear or front guards, then you could slightly change headlights or tailights, which would then would make them appear different.
The wondered if the shells are bought in from overseas. So, somebody makes them. Better to make 1,000,000 shells all the same, & sell them to the different car manufacures?
Just thinking this for a few years now? I'm probably wrong.
Unsure of the context, but for the most part even if you have a shared platform the vast majority of the metal differs between cars … some things like the Saabs and Vectras that shared a platform did apparently have a shared floorpan but totally different panels apart from maybe the glasshouse (I don’t think those Vectras & Saabs had the same turret & glass though - just the floor pressings, and I think different suspensions too).
You do have badge-sharing, or changes to a front-end as per the Benz dual-cab which was essentially just a re-engined Navara with a different nose & taillights. But for most platform-shared cars it’s stuff like the suspension hard-points, like how all Subarus are based on the same platform despite being different lengths, widths, tracks, wheelbases, and body-shapes. The “same platform” Camaro as the Commodore & Caprice has a shorter wheelbase than Commodore as another example, but a lot of the same suspension components will bolt in, and the panels are completely different.
The similarities you’re seeing are, IMHO, and kinda guessing at what you’re seeing, just a result or manufacturers trying to achieve a family look … similar to how the Insignia sold here as an Insignia had a lot of the same appearance details as a VF Calais, despite the two having almost no overlap (except maybe the fact the Insignia came with a 2.8L version of the V6 used in Commodores - albeit turbocharged).
Very few manufacturers that aren’t owned by the same parent company are developed on a shared platform though. For example BMW’s are based on anything else nor is anything else based on them … unless you include companies owned by BMW, as all MINI’s are BMW 1-series. Yes a current Chrysler 300 is based on a cheapened-down 1991 Mercedes-Benz, but that’s because Benz owned Chrysler before they realised their mistake.