We had a number of non-clogging pumps at our facility. Because these pumps were used to pump "dirty" water/fluids for various applications, they had an open-impeller design. I suspect (only a guess on my part), that they may be more susceptible to higher unbalance loads than other pumps (i.e. closed/shrouded impellers) used for cleaner applications.
I am not aware of any pump specifications that require a more robust design of the casing, bearings, shafting, etc. to accommodate increased loads for non-clogging pumps.
My suggestion is to rely on your trend data and comparison of similar/like machines to dictate your allowable limits