Apple Watch 6 for monitoring elderly parent - data retention

Apple's chat support function convinced me that I needed an Apple Watch 6 to monitor my (elderly) parent's health stats in real time and could achieve it by pairing my phone with that watch through Family Sharing. However I've just discovered that the health type functions like Blood O2, sleep, fall record (and many others) don't work via Family Sharing because they are blue-tooth-esque functions and will only work if paired with a local iphone.

So it seems to me that it is an either/or thing with Apple Watch -- EITHER my parent receives all the core health data on their phone via the bluetooth connection *or* I can manage their watch for them via Family Sharing and abandon the things that make this watch so good.

So my question is... how long with the watch hold the health data? If I see them (say) once a week and get my phone close enough to pair via bluetooth, will all the data download or is it too late? I'm most particularly interested in fall data (not fall incidents which result in alerts being sent out but the record of any falls in which emergency alerts did not go out) and blood oxygen. Also location services, I guess in case something happens away from home.

Anyone had experience with this?

Thank you!