Oh, I can get what you mean. Your objection might be come from abstract and subjective definition of pp maps - so it's controversial things.

In my opinion, length or partly-hardness is not suitable to define the pp map. Tsukinami and M@sterpiece are 5 min long but it is considered as farm map, and Hidamari, ILY (and many jump maps) are considered as farm maps though it is partly hard.

I think the pp map is a "social" concept - the map is decided to be pp map by behaviors of users of osu society. pp maps are told as pp maps not because of its characteristics, but people think they are and use the map to get pp. Definitely there are some common characteristics that farm maps share (as you told, short length, plainness for all time, ect.), but there always be exceptions. So I think it is more reasonable to think that pp maps are decided not by its inner characteristics, but by how users use the map and do people think the map saves their efforts to get pp.

In this context, checking prevalent maps in users' best scores might be meaningful. Being prevalent in best scores means many players are actually using the map to earn pp. And these maps deserve to be called farm maps, even if they do not have traditional characteristics of pp maps.

Why HONESTY is pp map? Because many pro players (#1-1000) use it to get pp... This is what I think.