One interesting thing I have noticed.
Because I'm tethering through the phone on a limited data plan I've been keeping a daily record of mobile data usage.
Looking back through that record, whilst I have been using the Phone as a mobile hotspot since the start of February its been clocking up 1.5x to 2x extra data usage compared to USB tethering.
I'm not doing anything different, nobody else can use that wifi except my laptop, so I'm wondering just why that extra use should be.
Maybe it's other passing phones trying to connect to the mobile wifi and so sending data back and forth?
That doesn't sound right but I do live in the towns market place, so even in lockdown there are a lot of passers by.
I may test that by turning on the hotspot, not connecting myself, and seeing what it does to data usage.