Proxmox needs to better their reputation right now if they're going to be counted as a contender, and burying the fact that you can have 24/7 SLA is not a good way of improving that reputation of being mostly for the homebrew crowd.
No. It took me less than 60 seconds to find it.
> ...the lack of it front and center probably scares away a lot of clients.
I've done on-call enterprise support for the products that I and the folks I worked with maintained and extended. We were whatever tier "the folks who work on the product" is. [0]
I can pretty authoritatively tell you that the folks who are scared away by a 60->120 second search to answer the question "It looks like this one vendor doesn't offer 24/7 support, but they do offer a list of certified support vendors. Do one or more of the vendors they certify to provide support and training provide 24/7 support?" are the sort of folks you rather don't want as customers.
[0] Tier 2? Tier 3? Who knows?