Clean blending only works easily when the effected signal comes back more or less in phase with the clean. That is by no means even likely when distortion and chorus among others routinely come back 180° out. Even working well it's hell murky compared to separate passbands.
Back in the day I had a very complicated fx rig that sent a high pass from crossover to the fx while the low pass carried on clean. Then there was a multi channel phase switching blender to take the two and reassemble. Depending on how many phase flipping pedals were on I had to switch which of the blender channels were employed. All this to avoid a dropout in the crossover range which was around 120hz, kinda important!!
This was pre Helix tech. Still a darm sight cheaper if you have the pedals already
The other advantage is it gives a single signal for FOH that doesn't need to worry about what jiggerypokery is going on.
The famous Mr Sheehan is possibly the most known exponent of the dark art. Even he gets pushback from FOH over a 2 channel bass.