To support what I’ve said further - This is a UV Sphere in Blender with 24 Vertical and 16 Horizontal segments.
When directly unwrapped in with the UV tools for Blender, the default Unwrap via Project from View with the face looks like this (without any straighting out the lines or so on).
Even when straightened out, the resulting decal would look skewed as the game engine has to fit each pixel of the image within the size of the faces provided by the mesh, according to it’s UV Map. This “squished” perspective of a section of the texture/decal on the faces of the mesh is expected, regular behaviour as the dimensions are not like that of the texture.
ROBLOX may not be able to solve this alone. This is equal parts ROBLOX’s meshes need to have clear UV mapping guidelines and developers utilizing textures need to be more attentive to the shape and scale of the mesh. If you were to skew/squish the texture according to the faces of the mesh it will be displayed on (say, using Adobe Photoshop’s or GIMP’s transform tools), it may not solve the problem but it could be less noticeable - on a mesh-by-mesh basis.
This is fairly generalized and I’m still learning about this stuff for my own game engine in university - there’s several caveats to be considered with the default “Face” placement of the decal/texture as well as UV Maps. ROBLOX has default behaviour for BaseParts, Unions and SpecialMeshes. When you create custom UVs and custom textures, you essentially help the game engine to unwrap and align the texture with all the faces which leads to better results.
I don’t know fully how ROBLOX handles the decal alignment to the UVs of each face of a part and specialmesh - e.g. whether it’s automated or specifically laid out with hard-limits built in by ROBLOX engineers so that decals and textures perform with mostly expected behaviors. Nonetheless, I would not consider this an engine bug given how meshes and textures work with game engines as a whole yet this is for ROBLOX Engineers/ Community Engagement to decide.