I've seen it on nearly every brand, I have some Lenovo Servers in the basement that also down-clock if both PSU's aren't installed.
I have alerts on PSU's and frequency for this reason.
The servers are so cheap that overcommitting them by double is still significantly cheaper than using cloud hosting, which tends to have the same issue only monitoring it is harder. Though most people using cloud seem to be happy not to know and it's been a known thing that there's a 5x variation between instances of the same size on AWS.: https://www.brendangregg.com/Slides/AWSreInvent2017_performa...
I have alerts on PSU's and frequency for this reason.
The servers are so cheap that overcommitting them by double is still significantly cheaper than using cloud hosting, which tends to have the same issue only monitoring it is harder. Though most people using cloud seem to be happy not to know and it's been a known thing that there's a 5x variation between instances of the same size on AWS.: https://www.brendangregg.com/Slides/AWSreInvent2017_performa...