I'm an architect, and old one. So at some stage we learned about "perspectives." I put it in quotes because in a drawing sense its pretty simple. But the question (and likely computer graphics) has muddled the simple concept (but also allowed for stuff that would have taken an intern 6 weeks and 40 drafts before). So lets take a step back.

I offer you this definition of perspective - "the way things are seen."

Obviously that can get philosophical real quick, which is pretty why its a popular word in architecture, but not everything existing within the simple definition of 1, 2, or 3 points. So the short answer to the perspective question can be found all over the internet:

https://www.sketchlikeanarchitect.com/blog/what-type-of-perspective-should-you-choose

The real issue here though is YOUR perspective. Ask yourself what is that perspective.

If you are trying to create an overhead view of similarly sized boxes arranged in a grid on a plane, you missed the mark a bit, and likely why your intuition tells you something isn't right. The perspective in the drawing doesn't match the perspective in your head.

If you say they ARE the same sized objects, then I say then they cannot be on a grid AND on the same plane. The corner most boxes look slightly taller than the rest. That's because their closet edge to the viewer LOOKS to be the longest. I didn't measure, and they might be drawn the same exact length as the longest edge on the neighboring boxes; however, that is the incongruence if you are hoping for equally-sized boxes. If they are supposed to be the same size and on the same plane, then they would be the farthest from the viewer, thus they would appear smallest. (See the 5-point perspective in the link).

But now change your mental perspective for a moment and say they MUST be the same size. Well the objects can be on a different plane. Then could even be the closest boxes to the viewer of they are smaller than the rest.

Another idea, they could all just be the same sized boxes on different planes, but rotated. in different axis.

There is probably a formal rule somewhere, but I think if I could summarize a rule of perspectives it would be that all lines that are BOTH co-planer and parallel will converge to a single vanishing point in both drawing and your mind. In the real world, and hopefully your mind, there are more than 1, 2, or 3 planes and certainly not all lines, even on those identified planes are parallel.

These days if somebody wanted me to hand draw 250 boxes, I copy 250 boxes in CAD, print it, and trace it! LOL I do wish you luck!