Messages sent from L2, on the other hand, are always verified to be sent with a gas limit >= GAS_LIMIT, which is set to 300_000. This value is sufficient to cover the gas consumed by the receiveMessage() function on the L1 deposit processor, which has a bounded and generally constant gas cost. The only exception would be edge cases such as warm storage slots, which could decrease the gas cost slightly.
Given the predictable gas consumption, it is not really necessary to provide a variable gasLimitMessage for L2 to L1 messages. The GAS_LIMIT constant or a more accurate gas limit can be used directly.
