Earlier quoted context omitted.
This is optimistic to say the least. I've worked as an SRE for 5 years and apart from the others in the team the devs don't have nearly as much knowledge. There's no way I'd rely on them to fix an outage. And even on a small retainer you'd better hope they retained the knowledge of how all that stuff works if you're only calling on them every now and again.
The idea is devops as _culture_ - I come in as an expert and set it up, then show them how I did it, then run through various disaster recovery scenarios so they learn it and can handle the vast majority of problems. And you'd be surprised how little problems you might have - I've had many VMs with literally years of uptime running without issue. Most people focus on "devops" as a job - and they never bother to teach…
Culture doesn't mean they'll know how to fix at 3am in the morning. The SRE with constant ops exposure is likely to have a much better chance, if only because they (ought to) really know how to debug it.