For no other reason than to inform, I checked yesterday after my latest run and I find that Garmin has been dilligently sending my data to Strava as requested and is fully up to date. Strava is keeping this data "safe" for me and appears now to have the entirety of my data from when I started using Garmin Connect and cycle computers and long before I obtained a wearable.
What this means in reality is that I can now switch hardware in future away from Garmin should I so wish without losing my history. My personal preference is a future smartwatch / wearable with eSIM as discussed elsewhere. Wbo knows what the future holds?