The die doesn't need the grease. The support block does because the tube slides through it while bending.

the grease on the die was to keep it from rusting. but I did put a little on the groove when bending. maybe that was wrong

Can't be too wrong. You built a whole car that way.
Besides, the die doesn't do any pulling. The forward clamp pulls the tube around. The die is just there to maintain shape.

I spray with WD-40 as its pulling .

that should work, doesn't take much

With the amount of force I found that it takes to pull C/M, I don't know if I would want to use something as thin as WD-40. And I did find that a little goes a long way.

I was using air over hydraulic. It did fine with no galling. I just spray the pipe and start bending 😊

Who knows, but I'll follow my instructions., besides, grease attracts dirt and grit which will scratch the tube and die then stress risers form, then all the extra work getting that mess off of everything, affecting the weld, no thanks, I'll do without it.

I did it for 34 years.. grease... wipe most off
with paper towel... if you feel anything I checked
with my fingers

No grease here. I do wipe the tube down to remove any dirt, grit, etc. And I pay attention to the dies and polish them as needed. Dirt, metal grit will scratch and damage the die and the tube.

I have never used any lube on a bender either