And MS has handed those keys over to law enforcement before.
some highly secure environments have connections comming from networks that sport windows. usually they will come in via something like a data diode so whatever comes in can physically not come out because its so risky to allow even such a network to connect to yours....
perceptions of what is highly secure can vary a lot depending on what a person has encountered. if you ever come across a place that is really secure u'll immediately know the difference.
ive never seen a highly secure corporate network and have seen close up what security is implemented in fortune100 etc. its a doozey. they just pay vendors with big retainers for IR etc. to be compliant and insured. that is not security. (and they spend millions on that which is funny as hell)
I have. We had an air-gapped network for ingesting and processing the deliverables and results of security audits and pen-tests at work. It was running windows and not Linux/BSD like the laptops of the pentesters, because most of our customers were MS shops so all deliverables we got from them were mostly documents, apps and files that were designed for Windows apps or had better compatibility on MS Office, and businesses stay solvent by conforming to their customers' needs instead of fighting them.
You could make your own BitLocker conforming to your requirements without relying on or trusting any cloud or corporate entity.
https://github.com/hparadiz/nexus-6p-biokey
I mean it's better than this sdcard thing at least.