Glue down mostly used on wood floor, engineered floor its also designed to be installed without glue.
Just install a insulation film underneath.
My preferred method for hard surface flooring is to always glue down. Advantages are that the glue can also be a moisture barrier, gluing down help reduce the noise of foot traffic, and also removes that air space between the slab and the back side of flooring. I have seen mold and mildew under almost every floating floor I have removed. Only disadvantage is that removal of the floating floor is very easy compared to glue down. There are some new vinyl plank floating floors that work extremely well to minimize the downsides of the floating floor I mentioned above.
I personally would install a vapor barrier and typically a floating floor. Also for other concerns as far as noise control or insulation research underlayments specific to your concerns.
If pad has any issues or concerns with leveling or unevenness a subfloor is necessary
I would float the floor. Movement of the slab ( such a an earthquake) a slight crack can transfer to the composite as it is one with bonding. Secondly a laminate floor is much more insullated and separated from the concrete if it is on a higher end foam pad. It’s also easier to replace a damaged slat or section in the future. The only time I would bond the floor is over a hardwood floor that can’t be refinished again to cancel existing squeaks.
Glue the floor down is the best method. The flooring will be solid and secure to the slab. Make sure the glues appropriate per manufacturer specifications. Biotic has the best glue and has a moisture barrier. You can do repairs to the floor as easily if its glued down to the slab vs floating. If you decide to float the engineered floor. You will need to use glue in the tongue and groove and install on a moisture and sound control pad. As far as movement (earthquake?) the transfer of crack in slab ? I’m sure he was confused with ceramic/tile etc. 2/3 homes we put floors in have or will have slab cracks. These typically need attention as they are from foundation settling. When its post tension slab they put expansion cracks in it. These typically need no attention and if they do you are limited on repair options. If you start to find large cracks in your engineered floor after being glued down then you have other issues such as RH (relative humidity), moisture, and or acclimation problems. Most of these questions can be answered correctly on the NWFA website. Make sure when you are making your selection on flooring it may be best to pick a contractor thats NWFA certified. I will post a link to their site for easy access. http://www.nwfa.org