Any SRE who does that is really filling a QA role. It's not part of the SRE job title, which is more about deployments/monitoring/availability/performance, than about specific functional requirements.
In a well-run org, the software engineers (along with QA if you have them) are responsible for validation of requirements.
well-run ops requires knowing the business. It's not enough to know "This rpc is failing 100%", but also what the impact on the customer is, and how important to the business it is.
Mature SRE teams get involved with the development of systems before they've even launched, to ensure that they have reliability and supportability baked in from the start, rather than shoddily retrofitted.
Without that it's impossible to correctly prioritise your work.