I admit, the GPS function will continuously drain (of course, it's working) but the idea that it should shut itself off means it will spend time and energy resetting itself each time you turn it on -- so, the lesser of two evils here.
Magic Lantern has a gps powersave option that turns gps off on camera off and remembers the state when turning it back on.
Back to the point -- at present, I shoot with all Canon gear -- and can't fathom missing a shot in the field because the lens forgot to adjust in some minor way. It's not like "horseshoes" where close counts - either the gear works as its designed, or it doesn't - and the opportunity for the "doesn't" (even minimally) increases when you interbreed brands. JMHO ...
I've also avoided 3rd party lenses so far, and have a bad experience with the Yongno rt trigger. Having said that, sometimes there isn't really much of a choice. For example. only Tamron has a 24-70/2.8 zoom with IS and its half the price of the Canon mk2. If given the choice between a Tamron lens or no lens at all, I'll take the Tamron :-)
Hmmm but there is no ML for the 7DII and likely wont be for quite some time. Further, use of ML has historically used more battery power due to more CPU usage to drive all of the enhanced functionality. So to say that gps save is a powersaving function is a bit of a "marketing" twist.
Also one of the things you buy when you pay the extra money is the time spent testing with other canon products. If Tamron spent the time to test their products with that care on every other system, then their price would be twice that of canon. You get what you pay for I'm afraid.