At one point the cells used by fast-truncate were called "proxy cells" and some traces of this terminology remain, e.g. WT_CHILD_PROXY in rec_child.c.

I was never clear on the origin of this term or what it was supposed to mean (the cell is not a proxy for a page, it contains a page...) and it had I think already mostly gone away anyhow before the past year's truncate changes. There are only a dozen or two references left, most in comments.

Getting rid of the last of them (e.g. changing WT_CHILD_PROXY to WT_CHILD_DELETED) will make the code clearer.

This is far from urgent or impactful but it's also not a large amount of work.