Master said:
Notice how while I get points when I convert black lums back to red in the PC version, I don't actually get health back unless I'm under some threshold. This is the behaviour I'm used to as I'm fairly certain the PS2 version also did this when I played Rayman 3 growing up.
Ohhhh boy, reading that brought back really terrible memories

At the beginning of TOTL2, you can convert one of the Lavicraft's black lums to break the following cutscene and trigger an IPG this way. I couldn't get this to work, and I spent
months trying to figure out why. Shoutout to the G.O.A.T. 1234, who realised that you actually needed the converted lum to heal you to break the cutscene, which meant that you could only trigger the IPG below a certain health threshold

I had kept trying it at full health.