This usually falls under "interoperability testing", but usually mitigated through your firmware rather than hardware. In the worst types of cases, you need to make sure your hardware works with some popular defunct vendor from 15 years ago since some big customers have used that hardware for 15 years, without issue, and will see your hardware as the problem when they plug it in.
For communication equipment, this is super important, with all sorts of "quirks" put in for vendors that didn't follow the spec. And, that includes keeping quirks in your firmware, so you don't break anyone else's. Imagine entire walls of legacy and long-gone and current competitor equipment, with robot arms to plug things in, and you have an idea of what some hardware validation labs look like.
Motherboard manufacturer firmware is also filled with quirks for specific CPUs, chipsets, etc.
For communication equipment, this is super important, with all sorts of "quirks" put in for vendors that didn't follow the spec. And, that includes keeping quirks in your firmware, so you don't break anyone else's. Imagine entire walls of legacy and long-gone and current competitor equipment, with robot arms to plug things in, and you have an idea of what some hardware validation labs look like.
Motherboard manufacturer firmware is also filled with quirks for specific CPUs, chipsets, etc.