I hear you, I have a Thinkpad (running Linux), a Chromebook, a Nexus 7 tablet, Pixel C tablet, OnePlus3T and a Moto G4 Play phones. Each has its foibles, e.g. my Pixel C seems overly keen to keep the pairing going, it will auto connect even if I tell it to disconnect, it keeps retrying. Compare with say my Chromebook which I have to manually select the Slims each time.
I recommend you just accept as a fact of life, BT is not as consistently simple as we'd all like, each local "stack" has its own implementation.
Could be worse... the Mini speaker I couldn't get to work at all in some of the devices (laptops specifically).