Recovery time suggestion for downhill skiing is laughably inadequate

I take your point, but I think the problem lies in what is meant by 'recovery time' - especially as like you say, it seems to be based on cardiovascular recovery rather than muscular.

But I think that's the way it should be - for example, I've cycled every day for the last 30 days and yesterday got to the stage where my legs could hardly cope with a 3/5 training session on Zwift, but my Recovery Time/Training Readiness that morning had said I was ready to go. But I'd argue that it was probably right, I could have comfortably taken on any activity that didn't involve my legs.

So even though your legs etc might need two days to recover from your skiing, it would be wrong for Garmin to say that your recovery time before taking on, for example, a swim would be two days when the limiting factor (e.g. muscular fatigue of your quads) wouldn't be relevant. Maybe a swim isn't the best example, but you hopefully get my point. I think what you're asking for is a recovery time that would only be relevant to the same type of activity.

It's always worth remembering too that recovery time is advisory before your next major activity (such as a race or all-out effort), not any activity. But I'd say it gives you an insight into your cardiovascular readiness, which you can't always feel (until you start an activity and wonder why it feels so hard) - but you also need to base your training decisions on muscular fatigue which is something you probably don't need a device to tell you.