Can you explain why you feel that the miners will completely ignore the RBF flag if it is set to disable? I know it is up to the miners but wouldn't they mostly stick to the intent of the feature? I know the incentive would be to earn more money but there are many cases where the miner returned excess fee as well.

Replace-By-Fee (RBF) is a node policy that allows an unconfirmed transaction in a mempool to be replaced with a different transaction that spends at least one of the same inputs and which pays a higher transaction fee.

Different node software can use different RBF rules, so there have been several variations. The most widely-used form of RBF today is BIP125 opt-in RBF as implemented in Bitcoin Core 0.12.0 and subsequent versions; this allows the creator of a transaction to signal that they’re willing to allow it to be replaced by a higher-paying version. An alternative form of RBF is full-RBF that allows any transaction to be replaced whether or not it signals BIP125 replaceability.