Viewing v21 eips in v23 is slow when loading folders of images

Wanted to pass this info along in case anyone else runs into it.  At work we upgraded our color correction stations to v23 and our photo stations were on v21 still.  We pack as eips and also send all of the thumbnails and cache along with the eips but found that v23 was acting really slow when viewing folders of images that were created in v21.  This created a lot of issues with the speed of our workflows and needed a fix right away.  We found that v23 was regenerating all of the thumbnails/cache for files even though they were there but were generated with v21.  I guess v23 won't use the v21 thumbnails/cache.  We upgraded the photo bays to v23 and the slowness stopped.  The color correction stations were no longer regenerating the thumbnails/cache and the speed was back.