I agree with Becca-- though the aerial roots may die off in the hydroton, I simply wouldn't worry about them going into the medium or not-- your phal will always grow aerials, whether it is round bound or not.
And it doesn't look like the pot is overly full to me either. 6 months isn't enough time to fill a pot like this. Several of my phals that have been in their s/h pots just under a year have yet to fill their pots though they have been thriving in general. Although, some have already started to mal-form their pots.
Just let it be