Actually, it's beyond subjective interpretation. Think of it as a set rather than several individuals. Don't think of the arboj, but rather as an abstract collection structure.
Ekzemple, let's say you want to group together members in a household. The household is the aro; the set. Once that is established, you can begin to include household members. Few members, many members, one member... it doesn't matter. What matters is that there is an abstract set called the "household", and within that set is members.
As another example, I'll use the Python language for readability. Imagine the following scenario:
aro = 
aro += alialisto
No matter how many members exist in the list aro, be it just "Alico", both "Alico" and "Benito", or even merging in a whole other list, aro is still an abstract collection which can contain members. It doesn't suddenly become a collection when it achieves an arbitrary member count. :) I hope that helps.
No offence, I think the above is awesome. However...
You know you are among nerds when you see a post discussing Esperanto with analogies to set notation and Python. You know you are a nerd when you read and like the whole thing.
Ah, but in Python, one can have an "empty" aro -- which is its state immediately after executing the first line, "aro = ".
Thus, a parcel that looks like a field could nevertheless be a forest in the sense that I designated it to be one, then went off to purchase seedlings, and will return to plant them -- and if you walk by in the interim, it would be the case, "You can't see the trees in the forest." (Apologies to Rocky and Bullwinkle.)
Por uzi la prepozicion "da", necesas ke la antaŭa vorto enhavas ideon de kvanto. "Aro" estas tro nedefinita laŭ mi por uzi "da" kun ĝi, oni ne povas respondi al la demando "kiom da arboj estas tie ĉi?" per "aro".
From what I see in my neighborhood, the only difference between a forest and a tree farm is the sign hanging on one of the trees that says "Tree Farm."
Another interesting fact, about 150 years ago, this region was 10% forested with many farms, but then people were tired of "growing rocks" so two thirds moved away; as recently as 20 years ago, it was 90% forested although lately people have been "planting house seeds" and making more open space.
I'm sure such things exist on a spectrum -- monoculure of trees, "managed woodland", limited logging in an established forest...
Years ago I used to say "save a wheat plant - recycle toast" as a nod to this idea that in some areas tree-pulp trees are grown on what is essentially a monoculture. I don't claim to have a lot of experience with that, but for sure, I've seen plenty of Christmas tree farms, and they certainly are not forests.
P.S. I had a hard time understanding your other interesting fact because of all the terms in "scare quotes".
If you will permit me an explanation, I websearched and found a few different definitions for scare quotes. I intended to use them in the following manner:
APA – The APA recommends using scare quotes “To introduce a word or phrase used as an ironic comment, as slang, or as an invented or coined expression. Use quotation marks the first time the word or phrase is used; thereafter, do not use quotation marks.” Oct 31, 2019
Unfortunately, I may have too tightly compressed my post and squeezed out its meaning.
During a visit to the state history museum, a docent described how, when large tracts of fertile farmland were discovered elsewhere, many rural towns were quickly depopulated as many people abandoned the very rocky soil here, saying, "They were tired of growing rocks."
Regarding "planting house seeds," that is an original neologism; however, I usually use it at the beginning of a longer observation that emerged from my visits with relatives who lived on farms and grew hay: the problem with planting house seeds is that nobody has yet invented a machine to cut, bale, and stack them at the end of the growing season.
Hope this helps.
Good point. Certainly the paper industry does a lot to build their case - including the term "managed woodland" which almost sounds like either a euphemism or an oxymoron.
Or maybe they're "green deserts".
Arbaro refers not to any group of trees, but is meant to evoke the idea of a complete forest and all the things that traditionally go with it.