WOTLK - Can't force the use of heirloom

I really love using Ask Mr. Robot while leveling my alts as it has been helping me to level them in the most effective way for years.

I just got some Heirlooms for my alts and in went to optimize my gear around them. Nevertheless it seems that the optimizer doesn’t allow me to force the usage of Heirlooms. Is that intended or a but?

Snapshot id: 6194f9bb47784ec79d92f875cd0c9a43

I think the heirloom is filtered out because it’s not getting fully parsed. It’s on my list to figure out how WotLK handles scaling heirloom items.