In principle I agree with you that an erase operation at the SSD level is likely to be significantly faster than host write speed capability.

Whilst I don't think the erase time is an issue for the WA calculation I'm still not sure how WA has been calculated. Somehow it does not seem possible that it can be so high, although the host write speeds imply that WA is being sacrificed to some degree.

It would be good if some of the key assumptions being made in the thread could be summarised in the first post.

It's interesting to see the difference TRIM has made to bluestang. Significantly faster write speeds and reduced WA.