I experience similar things with the Cavia. I was Rank 4 at the time of merging with the PC acc, reached Rank 5 on PC and after the final dialogue between characters, they seem to have reverted to the standard (Rank 0) quotes. I'll try it with other syndicates to see whether it happens to me as well and report back.
Also, the extra option unlocked after reaching R5 only shows when I play on Switch.