why dont all garmin fitness product talk to each other

You can record HR from Vivoactive HR on Edge, but you need to enable HR Broadcasting first.

There is no problem or defect to ‘rectify’

My queerer is why dont they talk to each other when they log activities on connect.

Because the products were never designed to work together, and there was never any promise by Garmin except in some product owners' imagination that they would work together such that the sum of the capabilities of what they bought is greater than individual unrelated devices.

ie the intensity minutes

Neither the Edge nor the vívoactive‑HR (I've never heard of a vívoactive‑HR+) is going to take the lead as the recorder of a sports/training activity, and engage and coordinate with the other device(s) to obtain what it does not have the capability to record by itself.

Garmin Connect will accept data uploaded from multiple Garmin devices, but will not presume records from different devices pertain to the same event or activity. (Using timestamps for cross-referencing is not entirely reliable when there is no guarantee, or ‘contract’ between devices, that the clocks on different devices are in complete synchronisation. It is also possible that the devices are not even in the same place physically at a particular point in time, if the locations by GPS of the devices are not in all the records, and therefore may not all pertain to the same activity. And so on…) There is also no way for the user to nominate two or more separate activity records (captured and uploaded by different devices identified by their serial numbers) as pertaining to the same activity, and use the data to enrich the source-of-truth record of the activity by combining, de-duplicating and resolving inconsistencies in different attributes.

You want what you want, but it doesn't mean it's easy, or that you should have it when that wasn't promised and isn't owed to you.