Why does LP cover restoration have to be so difficult ? The actual answer is to simply use the glue (of your choice) and glue the cardboard parts together.
If regluing was done to your satisfaction,than it is of no consequence. However, if we are considering re-selling than the discussion changes.
I use archival products; curator approved tape and glue. Of course, I own a collection that many would die for(stereophile "tang"). But that's me. For the person who just wants to glue the cardboard together, Hey go for it. There is no financial consequence unless you intend to sell what you own. LP grading systems downgrade certian fixes. In fact, it probably best on certian select items to leave them "as is" and take your chances on the secondary market. Besides, no auction house that I know of does business with 99% of what's in consumer hands. Remember,just one scratch can reduce the value of a recording by 99%. So, "do what you will", keeping in mind the resale consequences. All the best.