In __wt_value_return_buf, we unpack on-page values depending on the page type and check the visibility of the time pairs that were extracted from the cell. In the case of a fixed-length column store, we don't have cells. Instead, we have a buffer and a recno which we use as an offset to access our value. We need some way of determining visibility of on-page fixed-length column store values since this information isn't retained as part of the on-disk format currently.