Like the telephone game, the more transitions the more that can get lost. My guess is the cube has a combination of flat & smooth shading. Somewhere in the work flow seems the entire mesh is flat shaded.
Both Blender & the Blender .babylon exporter do mixed shaded vertices.
This can be changed in Blender. Not sure your goal. The other thing to note is the difference in file size.
Ok maybe i will take a look how to change it in blender. For now it’s not such a big problem, just not so nice to look at… I would guess the different file size also comes from, that blender only exports is at one mesh and the sandbox does like 8 meshes. Like one for each side, and the hole also has two.
Idk maybe i find out how to set blender to also export smoother and in 8 meshes, because i actually prefer/need them… but yeah babylon sandbox does even different weird things like inverting the coordinates because my gltf files are bad? But blender also fixes that somehow to be right again…
They are really hard to work with. The exporter is programmed to handle them, but they cannot be mixed with the other 2 (flat & smooth) in the same mesh during export. I only had one crude example that I had to make myself, when I basically re-designed the exporter for 2.80. Not working perfectly, as you have seen, but I do not want to touch that stuff.
For geo actually built in Blender, I have to imagine everybody does the Blender 2.80+ techniques I described above. It is dead simple.
You can clear it on a single mesh clicking on the item shown in red, which I did. I then decided that stuff really needs to be joined. 42 meshes for just this tiny thing is insane. So after I changed the cylinder, I tried to join everything to reduce the number of times of clearing the normal data. Blender immediately terminated!!, which does not happen often.
I have not done anything more since, like :
joining while everything was still "split-normal"ed, or
Additional: I am really surprised that Blender’s GLTF importer even maintained these kind of normals. How did you even get this into Blender? I could never get your .gltf / .bin to import. If you imported some other way, switch to trying to import a .glb, might be another way to go.