Yeah, after b4evrtru26 left their comment, I hopped in-game to do a sanity check, and discovered that aspect of the mod.
I am decidedly not a fan of having two separate pieces that really could just be one piece, like how Modpack and MJM do it. It'll be annoying to juggle more pieces on the hotbar.
But that's mostly just nitpicks on my part, and not a complete dealbreaker.
I might utilize New Legend more in the future, since like the wider selection of panel pieces it has. The 1x2 and 1x3 triangle panels open a lot of possibilities for instance, plus I've been starting to use its thin pipes for handrails and the like more recently.
But, I doubt I'll switch completely since the other mods have a much higher convenience factor. At least for me, when I'm in the process of building.

The New Legend Mod hsa different parts that are labeld R or L for left and right so they could be mirrored, Its not as easy though but possible

Maybe, but I don't like using New Legend for anything but the aesthetic pieces, like the steering wheel, pedals, lights and such.
The panel pieces in it often rotate weirdly, and in a few cases, aren't able to be mirrored, due to limited rotation capacity.
I tried using the 1x2 triangle panels from New Legend for the bucket, which worked well for the right side of the bucket, but since they couldn't be mirrored, it did not work for the left side of the bucket.
Also, the majority of pieces have a weird tint to them, making it so that when you recolor them, the color isn't correct.
Take a Modpack Polygons piece, put it next to the corresponding New Legend piece, color them both yellow, and you'll see that the Modpack piece is actually yellow, while the New Legend piece is orange instead.

Maybe I could have done this exclusively with New Legend pieces, if I worked around that mod's jankiness, but I didn't want to make this in any way other than what I envisioned.

you could do the same thing but just with new legend mod