Partly it is, but there wasn't much hope to convert those to RHEL. The plan was:

1) to offload the production of the releases (effectively what is now Alma Linux). Because there's so much use of CentOS, it was pretty much a given that somebody would pick up the slack. Most of those companies weren't running stock CentOS anymore, they had their own downstream repositories

2) to give more insight into the making of RHEL minor release to CentOS SIGs and to companies that run CentOS derivatives

Facebook for example does not use the RHEL kernel and was one of the early adopters of CentOS Stream even before CentOS Linux 8 was terminated.

I know of companies with millions of servers that switched to CentOS stream instead.

Yes if you have millions of servers you would be using Katello (open source Satellite) anyway and then you only have advantages from CentOS Stream.

NB CentOS was given the EoL date in 2020[0]

There is a difference between CentOS and CentOS Stream

https://blog.centos.org/2020/12/future-is-centos-stream/