Feels relevant. OP_RETURN is configurable via bicoinds -datacarriersize flag. It is not technically a consensus rule.

Samurai uses OP_RETURN for both its bip47 paynym and Whirlpool Tx0 construction. The 46 bytes in the whirlpool OP_RETURN contains info to allow the Whirlpool server to verify that a user has paid their fees. Samurai probably does it this way because the limit was increased to 80 bytes in 2014 and hasn't really been changed since.