However, many of us feel this is a particularly bad rule, based on only one recorded incident where skirmishers got imbedded into another formation. Skirmishers moving completely through friendly infantry formations to get away from the enemy was a standard practice during the 'classical' era, and probably during the 'dark ages' as well. There are no recorded incidents of the Greeks, Macedonians or Romans suffering this type of formation disruption by their skirmishes moving through the lines, they had military manuals detailing how it shoud be performed for god's sake!
I can see where if you have a very deep formation this would allow the Ps to move much further than even its normal tactical move. The counter to this is that it then is unlikely to be able to get back into combat if it needs to.