Not my experience at all! Are you quite sure you weren't simply driving something else into clipping downstream?
I will second that as well. If I run Bass > LPB-1 > PJB Combo Amp, nothing but clean volume. It's a powerful boost though so you can definitely send stuff into clipping/distortion.
Some clean boosts don't give you much boots even with the knob all the way up so the LPB-1 can feel like it does not stay clean when in fact it is just giving you a LOT of clean boost. You would get very similar results with high gain clean boosts like the SFX or Lizard Leg boosts.
Now is the LPB-1 as good as the SFX or Lizard leg? No. Is it as good as a lot of other higher priced clean boost pedals, yes.