afik if both data lines are low level this mean SE0 and ANY device peripheral or host ( even host ) can't use data channel.
if a peripheral is inserted into a host receptacle this is signaled by pulling d+ up so this differential "1" mean session can be started.
from peripheral POV those :R keep d- low for charger detection and d+ low for not initiate SRP because phy is MASTER on ulpi ( DIR signal is output on phy )
so all make sense