Envelope Distort using a shape with 4 points as a top object generates an unexpected envelope
Text and envelope distort bug still needs work.
I've seen this reported before but it is strange why it has not been addressed in the latest version of AI, the envelope distort with top object will warp text for example, incorrectly, if the bounding object is at a certain angle. The workaround is not satisfactory because the bounding object must be rotated more horizontally to the text, resulting in an env. distort that's not the intended effect. Please see examples of before and after: one is correct (had to derive from CorelDraw), the other is not (AI).
Another issue is the resulting distorted texts' bounding shape is automatically converted into a curved object. It does not retain the original bounding shape that had only straight lines.
A workaround we can use is a dedicated button to create a correct mesh from a path, in a free MeshTormentor plugin panel (a must have tool to work with meshes in Ai and to stay sane doing that): http://www.meshtormentor.pp.ua
But yes, it’s amazing Ai tries to create an orthogonal-looking mesh from an obviously rotated quad and gives no control over the preferable node positioning the way the plugin does.
A generally similar problem: https://illustrator.uservoice.com/admin/v3/ideas/34342096
Several other related problems discussed in the comments.