Personally I think forms are a portion of the formula:
There are forms- teach rudimentary movements, concepts, body co-ordination, attributes etc...
Then the forms concepts have to be trained with an partner to get the body mechanics and interaction with another skilled practitioner.
Then they have to be tested in the ring or full contact with a partner or opponent that is training relistically. (not saying to perform a form in the ring, but the mechanics and concepts have to be exprienced)
As for mutations I think they exist based on experience levels and interactions that the practitioner has had. (of course as stated before memory is 1 variable for this)
But also whats wrong with changing up some of the movements? Just as long as it doesnt violate the principle and concepts that are being trained in the form...
I've seen countless variations, but I feel they exist for a reason.
Just my take on this.
Nothing is harder to see into than people's nature. The sage looks at subtle phenomena and listens to small voices. This harmonizes the outside with the inside and the inside with the outside.
--Zhuge Liang--
樱花瓣在飘零 这悲凉的风景
长袖挥不去一生刀光剑影