Regarding excursionist perk difficulties, note discussion in the omnibus questions thread, starting from this post:
https://www.flyertalk.com/forum/36693709-post787.html

It seems that there has been a devaluation to disallow same-cabin excursionist redemptions. Per the wording, excursionist is only allowed for a lower cabin, i.e. J-Y (excursionist)-J or F-J (excursionist)-F.

https://www.united.com/en/us/fly/mil...ir-awards.html
https://web.archive.org/web/20240926...ir-awards.html