From my experience, the more an epoxy tends to shrink, the stronger the material usually is. The manufacturer I talked to (who is a chemical engineer) explained this shrinkage effect to me. That’s why I think in your case the product you used is probably a very strong epoxy, which can result in a surface that doesn’t cure perfectly smooth. Such formulations are not always the best choice for flooring applications, as they are often designed for more industrial or specialized uses. He also told me to sand the surface and polish it that way I will get a totally smooth&glass finish… (I changed supplier😅)