There appears to be a considerable amount of confusion regarding this. A FRTOL is no longer an ICAO licence, consequently, there is no ICAO requirement to include English Proficiency on such a licence if an individual State continues to issue them.
It was a UK CAA decision to grant Level 4 to all UK pilots who needed such an endorsement on their pilots licence for International use (no requirement for National use!). Passing the practical RTF test indicates that the candidate has demonstrated English Language in a practical manner to at least Level 4, consequently that was the level granted in the UK. Quite why the CAA no longer accepts this for initial tests is beyond comprehension as it is probably the best test of compliance with the ICAO requirement anywhere in the World!
The Indian DCA are responsible for English Proficiency endorsements on pilot licences that they issue, holding a UK FRTOL really has nothing to do with it, there is no endorsement upon it, there is no ICAO process to endorse a non ICAO licence and the level 4 granted by the UK CAA was for their own internal use.
If an Indian applicant asks you to sign a SRG1199 it is of no relevance unless he also holds a UK pilot licence, which most do not. If he undergoes a RTF test to renew a UK FRTOL then the examiner can issue a Level 6 on the SRG 1106 provided the candidate is fluent. In 2006 the DCA India stopped accepting the UK FRTOL for conversion to an Indian equivalent unless it was accompanied by a UK issued pilot licence so there is really no valid reasons to receive such requests. They continue nevertheless!