Using bpp ... not so good. The idea was to calculate a size suitable for any possible codec.
Of course the calculation could of course be fine-tuned according to the used codecs.
However it does not hurt at all. The client is always free to honor the setting or to sent something lower - at least in non-rfx mode. in rfx mode the client must use our setting (or a larger value) according to the specs and in that case the calculation is currently fine