Thicker epoxy rather than grinding concrete substrate to achieve smoothness
The 3 mil (0.003 inch) thickness in the product documentation is about the same as the thickness specified for an automotive epoxy primer I worked with this summer. For comparison, I sprayed that product onto steel that was prepped with either sandblasting with 80 grit media or D/A sanding with 320 grit screen. It came out fairly smooth -- certainly there's no texture from the metal showing through.

Your description of the concrete ("laminated rice") makes it sound like the chemical treatment entirely stripped the cream off the concrete and has left you with exposed fines (sand). Eyeballing a caliper here I'd guess that must be a profile of at least 20 mils. It would take a lot of coating to fill that.

The roller will lift a lot of paint back out of the depressions in the surface. A squeegee wouldn't do that, but I wonder what happens with a very thick coat. Does it cure properly? Does it bubble/blister when the solvent evaporates off the surface but more remains below? The vendor may have some guidance. You could do a test section.

It seems to me that grinding isn't inherently awful unless you do it dry. Grinding with water will make a sticky slurry or paste but zero dust. Don't leave it to dry though. Dilute the paste with just enough water to be able to push it around with a fine broom or a squeegee and pick it up with a wet/dry vac (resist the temptation to wash it down the floor drain). Apply fresh water, ie rinse and repeat, until the paste/slurry is removed. A pump-action weed sprayer or a garden hose with a misting nozzle could be a convenient way of applying the water.