Does non-sanded grout require 2 coats?

I have NO IDEA what this person is thinking of. If, that is, they have ANY experience. I mean no offense by that, but.....

Cement grout is commonly used for wall tiles and other small gaps. The rule with cement grout is to use it for joints measuring 1/8 of an inch or less.

Sanded grout (wall grout+fine sand) is used for larger gaps as the cement version often shrinks in wider spaces, leaving an unfinished space. The sand acts as space filler so the grout won't shrink down on you during the curing process.

Another thing to notice is what type of grout you're working with vis-a-vis surface area. Some grout needs a slightly moist surface, while others will only work when applied to a dry surface.

Non shrink grout (a.k.a. cementious) sets rapidly, holds firmly, and, best of all, won't shrink during curation. The grout materials offset the natural shrinkage in the cement. Note that this advantage may also result in volume increase over time, so be aware of that when leaving for long-term storage. Non-shrink grout is used for 1/4 inch- 24" deep gaps and most commonly used for equipment base plates, columns and rails (to swallow the vibrations and heat, although not extreme vibration or temperatures) and anchoring bolts. Be sure to get a quality non shrink grout as some of the cheaper ones are made with metal fillings, which corrode with time, leaving gaps in your grouting.

If you have any further questions, please write to me

Grout Shrinkage

I have never heard of grout (either sanded or unsanded) shrinking and requiring a second coat.

Apply the grout as indicated on the instructions and clean carefully with a thoroughly-rinsed and wrung out sponge. Be certain to press lightly. You don't want to dig the grout out from the grout lines.