I agree 100% that is a pie and this is a tart
I think that is quite right by contemporary standards. Tart and pie are quite fluid. My usual apple pie recipe, as it appears in Ancient Cookery (1381), is described as... For to make Tartys in Apples: Take good apples and good spices & Figs and raisins and Pears and when they are well braid colour with saffron well and do it in a coffin and do it forth to bake well.
(coffin means a bread crust, BTW, is not some goth thing)
Usually with early recipes pie was savory and tart was sweet. So eel pie, beef pie, liver pie, pot pie, etc... while apple tart, peach tart, again etc...
we also have tort, which I generally think of as dense flour heavy tarts, with chocolate or some such to make them homogeneous instead of with chunks.
American Apple Pie, which started as an Appalachian thing, making a meat pie with chunk apples, set the view for American pies, I now think of a 'pie' as simpler, chunk ingredients, generally crust + filling construction without a lot of elaboration. Tarts are a bit more processed, and have internal consistency, i.e. not chunks, but a consistent filling. And torts are smaller, and quite refined.
So sweet pies for me are the pickup trucks and suv's of the dessert world, tarts the sporty coups, and torts the two seat sports cars, when you also might see a souflee or some such.
Each has its place, we even have a crisp or a coddler which is a step less refined than a pie in my view, but still tasty, great for campfires and when you don't have a consistent heat source.
Lemons, I say as an ingredient, are most useful in the tart to tort area, as, well, they are much sour and acid, and don't chunk well, like an apple or pear might. So I'd even if I made a lemon merraingue pie, think of it as a tart traditionally, but the nomenclature is fluid and we do think of that as a pie. Again key lime pie also, I think should be a key lime tart, for consistency, but called a pie. Same with pumpkin.
I say as a rule of thumb, the less you do to your ingredients the more you are in crisp/coddle to pie the more you do, and the more separation you get into tart and tort.
The end of this is, trained linguists are still pouring over those four (or five) words, and it also varies culturally. I like reading old recipes and in the European and British tradition most of which they call Tartyes we would call pies, and most of which they call Torte, we call a tart.
I've even confused myself now, and not gotten into meat pies. I am now working on a medieval eel pie recipe (yup I got eel, and due to my wife making a tragic bet that really overestimated her view of the american electorate, the unthinkable has happend and if I prepare an eel pie she must join me in eating it). Eel, of course is not an everyday food for us as it would have been for a medieval peasant. I have some in the freezer, that I had to go to lengths to obtain. But eel, fish, meat, and fowl pie were the thing at least through the early elizabethan. A lot of things were called Tartyes as they were sweet not savory.
My $0.02.
Cheers,
TBS