DTS MA 7.1 - seems to be playing 7.1 but shows as "5.1 (side)" when I press information

For years I’ve been encoding MKVs with Dolby True HD soundtracks to FLAC, but didn’t remember having an issue with 7/1 DTS-MA tracks. I’m hearing rear surround activity without a matrix selection, but when i press “I” for information it lists any DTS-MA tracks as 5.1 (side). If I re-encode the same MKX as FLAC it shows as “8 channels”. Am I missing information if I don’t encode DTS MA 7.1 tracks as FLAC?