Of course, but marketing is marketing; if you blindly believe marketing headlines before doing your due diligence, I'm sorry to say, but it's a bit naive. If you look at pretty much any protocol out there that's implemented by multiple vendors, there are all small nuances and incompatibilities. Even extremely detailed specified protocols have incompatibilities; S3 not having a formal specification should make you expect even worse.

If you look at S3 implementations from the various clouds and NAS appliances and whatnot, you'll see that none of them is a 1:1 compatibilite with each other.

If you wanted to warn others that, instead of Minio not providing "full" S3 compatibility, but Minio does not provide S3 compatibility at all (which is what the title edit suggests), then I believe you are mistaken. Minio definitely provides S3 compatibility, all the main tools and SDKs can talk perfectly with Minio, it's just that there are different implementation details around the edges.