My mono "Kind of Blue" has that limp plastic inner liner as you described. What you have is an original release. If the side 2 track listing had been incorrectly inverted, that would make it an early pressing in the run before they corrected the jacket (mine is that way).
I have no idea of the collector value of a record with an unbroken inner seal, but, if you are concerned with mold, it might make sense to open the record and clean it thoroughly. Columbia was a big label that put out a large number of records for each release, so the original "Kind of Blue" is not extremely rare.