[DanDan]

Like any tool or instrument, results obtained are dependent on technique and operator skill. A rotating boom cannot randomise VLF. However one can move the boom centre to various different carefully chosen locations.
The use of multiple locations or sometimes even multiple microphones is common I believe. I am not sure that rotating booms are often used in the big rooms, I have seen and used them in smaller semi rev rooms. Multiple locations can extend downwards the validity of the spatial average, plus of course the spectrum of useful results. A room can only be certified to a certain frequency, directly related to it's size. That does not mean the room is useless below that frequency. With ingenuity and skill one can get useful results, certainly in comparative tests.

DD