When I picked up my 991 I explained the situation like I did here and the service rep made a battery check.
These are the results:

 

That’s not a stellar report. Did they charge the battery afterward?

What model year is your 991? How old is the battery in it? Is it the original?

Car batteries last 6-ish years in general. Most, if not all, 991s should be on, or close to battery #2 by now.

 

I had that feature on a 2001 Mercedes SLK. I don't think it is a USA thing. I never used it.

 

My US 88 911 has it. Been on US cars forever.

 

As long as a street is not marked as "No Parking" (circle w/line thru it, or circle with X thru it and no yellow lines) you may leave a vehicle as far as possible out of the drive lane on the shoulder. You select the side(turn signal) nearest the street and leave that side illuminated. It lets others know the car is stationary and likely unattended and to plan for oncoming traffic etc. (my experience in England Germany)

Interestingly, I've noticed on my car 14 C4S, if the voltage drops sufficiently, the system seems to go to sleep(parking lights etc) and will restart as normal with functions returning after the restart.

 

The one-sided parking light function, turned on by leaving the turn signal up or down, has worked in all my Porsches back to my 914 in 1970.

 

Yeah, I guess it's a feature, not a bug, even for US spec cars. I didn't know about it at the time, but I must have bumped the turn signal stalk after parking the Panamera and was baffled for several minutes by that single tail light that wouldn't turn off even after all the other lights dimmed and went dark. I never tried it on my 911, but I guess they have this feature, too.