FTS Improvements in CB 7.x

This ticket is for documentation regarding FTS index disk utilization improvements in CB 7.x. 
As confirmed by Jon Strabala and Abhinav Dangeti (in fts slack channel), there is no documentation or release notes with details around improvements in disk utilization for FTS indexes in CB 7.x. 
Keshav Murthy shared feedback from actual customer with 90% drop in disk space in CB 7.x. We could potentially use documentation, release notes and/or additional details for other customers using FTS in production.