The code in __wt_leaf_page_can_split uses maxleafpage to make a decision about whether a page is big. I believe it intends to use maxmempage instead.

The maximum leaf page is likely to be 32k, wheras the maximum in-memory page is likely to be 10MB.

The code was introduced in WT-2954, here is a link to the patch

We should do some more spelunking through history before making this change, to ensure that it's a bug and not expected. If we determine that it's expected the comment should be update to be clearer.