What is this dumbbell looking symbol on this schematic? (looks like jumper pad, but with a short)
It's a solder jumper. Just like two header pins with a shunt cap, but cheaper and more permanent. Bridge with solder if the connection is desired.

I'm not sure why you wouldn't in that case though unless there are I2C pull-up resistors already present elsewhere on the line. Seems like it would take the same amount of effort as just removing/not populating the pull-up resistor.