I have a kitchen aid artisan with 300W and have read conflicting opinions on what it can and can't do. Many seem to have a hard time using meat grinder and food processor attachments, because of the low power. Is this the case, or does it simply take longer or require more prep (precutting the meat into smaller pieces for example)? What kind of meat would it have problems with? Why would it have issues with a food processor, which only cuts relatively soft vegatables? 
I am not so sure that it is a secret to next-level BBQ.  Several BBQ discussion boards, as well as Reddit, have explored this topic.  It seems that it is mostly done as a matter of convenience.  For example, when purchasing a large quantity of meat (like at Costco or other bulk store).  Many will season everything, and freeze what they are not using, to be thawed and smoked or grilled at a later time.  I did not see any reports of culinary advantage, other than convenience.  Though some even have smoked from frozen, which, of course, extends the cooking time.  I guess the disadvantage would be if you decided you wanted to use the cut for a different purpose.  You are stuck with the pre-seasoning. While this was not discussed, I might be worried that a seasoning with salt in it might create more of a cured texture on the exterior.  That might be desirable or not.  Finally, irrespective of seasoning, freezing and thawing does have the potential to impact texture.  Particularly if it is done more than once.  Again, maybe good, maybe bad, depending on preference. 