back seat
1 seat at the back of a car, etc.
2 (idm idiom) a ,back-seat `driver (derog) passenger in a car who gives unwanted advice to the driver A passenger who points at the driver indiscriminately.
take a back seat (fig metaphor) behave as if one were unimportant; take a less prominent part in sth pretend to be an unimportant role; play a lesser role in something.
The latter idiom is a metaphor, in line with pointing passengers.
The meaning here in idc_whitepaper_0101.pdf is that this interoperability problem will also have a place, although it may not be important in terms of functional use.
In addition, the introduction of a “standard” implies that interoperability issues take a back seat.