The core community maintenance is one of the most responsive and efficient that I've every worked with. Therefore, if they love to shout about day 0 support, I think they have the rights.
The provider project I've contributed to, or better, tried to, has been a complete trainwreck. Many devs discussing on an issue, maintainers ignoring the issue for a long time, then maintainer stepped in with a fundamentally incompetent comment, then disappearing again. This is odd, because the provider is maintained by Hashicorp employees.
There are polite and communicative ways of explaining why it's not possible to work on a fix/feature; that maintenance was far from this.
I suppose that they Hashicorp has a specific plan of maintaining the core very actively, at the cost of doing very poor maintenance on the/some providers. I wouldn't be suprised if they put their less important employees working on the providers.