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.
It's also worth noting that Borgmon readability included an awful lot of "how not to shoot yourself in the foot in strange and unexpected ways". That required someone who had shown they knew of those strange and unexpected ways to review your code.
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.