I've used the release party approach, and it works, at a high cost. I've also worked with really good QA teams. The best ones don't really test contracts, they test the contract itself - that is, instead of testing that the UX behavior matches the "expectation", they pressure test that the "expectation" matches what a real user might do.
But even in these places, I still find value in having a second set of eyes pull down a PR and see if it makes sense. With good tooling it should only take a minute or two (and without good tooling, investing in this tooling usually helps a ton of other places too). This saves time in the ultra-expensive "30 sets of eyes pull down the product and use it" party phase, and frees up QA to be even more effective at pursuing edge cases.
Plus, again depending on the company, often fixes forward from mainline are kind of expensive, especially if you work in B2B / Enterprise where change management often works on a cadence. Fixing the feature on a branch can be a lot cheaper and easier than fixing it once it's in the wild.
Anyway, it all depends on the team and their process, and I'm far from a zealot about much of anything, but I do really encourage pulling down PRs and clicking through them as a matter of course, regardless of what additional mechanisms are in place.
But even in these places, I still find value in having a second set of eyes pull down a PR and see if it makes sense. With good tooling it should only take a minute or two (and without good tooling, investing in this tooling usually helps a ton of other places too). This saves time in the ultra-expensive "30 sets of eyes pull down the product and use it" party phase, and frees up QA to be even more effective at pursuing edge cases.
Plus, again depending on the company, often fixes forward from mainline are kind of expensive, especially if you work in B2B / Enterprise where change management often works on a cadence. Fixing the feature on a branch can be a lot cheaper and easier than fixing it once it's in the wild.
Anyway, it all depends on the team and their process, and I'm far from a zealot about much of anything, but I do really encourage pulling down PRs and clicking through them as a matter of course, regardless of what additional mechanisms are in place.