I don’t know about your brand of tub. I believe some companies tried to recover motor heat into the water with different ideas.
Most new tubs now I believe don’t have blowers for air bubbles and rely on water jets that admit air into the water stream. My tub has a blower along with two pumps that have different speeds. We like the blower and use it mostly in the summer, as it tends to cool the water. If I have the tub set to 104 in the winter and we have friends over not used to hot tubbing they sometimes feel it is unbearable and I will lower the temp to say 102 and run the air gets for a couple minutes and the tub is more to their liking within a half hour.
I’m no expert on heat exchangers in tubs, but I think they are just a supplement for an electric heater. I don’t know how much help they really give.