I have been using Sync for a few years now. When I first started, there were a couple weird issues. When I reported the issues, they responded immediately and actually fixed them. I have zero complaints about them so far. I don’t use Windows Explorer so I can’t comment on that.
The telecoms are using bad-faith interpretation of the new rules to require their customers to buy (often identical) phones directly from them. This is a corporate money-grab and it needs to be aggressively addressed.