I think the discussion is relevant as many folks mix speaker types (passive and active) together and use various electronics in the chain.
You do need to keep in mind that any DSP (whether in the speaker, an amp or in a DriveRack type device) induces a minor delay in the signal .. only an issue if you have different chains to your subs and tops.
For example, if you use a powered top and a a passive sub(s) with a normal amp, the signal will reach the sub driver BEFORE it reaches the top drivers due to the inherent delay in the DSP section of the tops. It may be minor, or it can be as large as 5-6ms, which equates to about 7-8 feet of distance, so things might sound muddy. In that case, using a DSP in the sub amp (or putting a delay in the sub path) may help clean up things.
It's not wrong .. just need to be aware of your entire chain.