The passive radiators do not effect how close the speaker can be placed to a wall.
How close a speaker can be placed to a wall is function of the amount of baffle step compensation of the speaker. Basically, there is a 6 dB “loss” in the bass of a speaker as it transitions to being omnidirectional. Placing it near a wall boosts these frequencies (below about 350 Hz on a speaker with an 8” baffle like an FR5).
Placing a speaker near wall also causes more reflections and comb filtering that hurts the localization and imaging, even if you make a speaker tonally try to work near a wall, there are these cancellations to deal with.
We can voice the speaker with less low midrange and bass, but this would limit people who want to pull the mouth from the wall a bit more. That is one of the benefits of an active system (more adjustability here).