That's a fair take and distinction. Same re: GPS, lol. I'm shamefully bad with directions.
I thought the same a few years ago, but I've come to appreciate how wildly out of touch people can be with their bodies and minds and, in some cases, only in very specific ways.
E.g. myself - I've been training for 20 years, I'm attuned to most aspects of training, what foods agree with me, how my response to both has changed over time...tons of examples.
Stress has been a different beast, and it's been quite helpful having a couple of reliable metrics when my default is to tell myself I'm fine and don't need to sleep more, wind down from work earlier, etc.
Example of how this might actually play out - If I was coaching someone who was following their plan to a T, and they told me their strength was dipping, their digestion suddenly felt off, and that they were mentally foggy - it'd be useful to look at their HRV and RHR over the last week or two. If those were off relative to baseline, we might end up talking about recent stressors - work, life events, relational stress, etc. - and then it'd be highly likely that conversation would lead to an "oh shit, I have taken on a lot more stress recently" kind of realization. And then we could adjust accordingly.
Could that conversation have taken place without using the metrics as a middle man? Sure - but people are stubborn, and none of us is as good at connecting dots as we'd like to think. So IMO a little extra data helps.
Key phrase, "a little" - not 20 different metrics to mentally masturbate about.
