There is absolutely nothing malicious or suspicious about deciding not to provide docker images or binaries. Doing so does not hide or guard you against CVE's, which are entirely unrelated to such optional processes.
Building minio is not only trivial, but is standard procedure - the latest release is in my distributions standard package repo, and they would not use prebuilt binaries. If you want that dockerized, the Dockerfile is shorter than the command-line to run said container. Dealing with Docker themselves, the corporation that has famously gone on a tax collection spree, is however quite the pain in the arse for a company.
I can't stand the entitlement people (everyone, not one particular person) feel when they are provided things for free. Sure, minio is run by a corporation these days and this applies a bit more to smaller FOSS projects, but the complaint is that the silver spoon got replaced with a stainless steel one. You're still being fed for free, despite having done nothing for it.
</rant>