Of course, changing MakerNote data is risky. But it is worse: changing any data is risky if you are interested in MakerNotes.
EXIF consists of several arrays of records with an integer for tag ID, an integer for the tag size (bytes) and an integer for the tag data. The tag data, however, are written within the record only if the byte size is at most 4 - in all other cases the tag's data are written somewhere else, and the data field contains only the offset to the data. This offset refers to the beginning of the EXIF structure.
And this is the problem: Many manufacturers use the same structure within the MakerNote record - i.e. write offsets from the beginning of the EXIF structure, not relative to the beginning of the MakerNotes. This means than, when for example there is a Description record (which is a well-documented standard EXIF tag) before the MakerNotes and you edit the description the MakerNotes will shift by some bytes - but the tags within the MakerNotes still are seen relative to the beginning of the EXIF segment. To fix this a program must decode the entire MakerNotes and after editing it must rewrite all MakerNote tags with their new offsets. If this does not occur decoding of the MakerNotes of an edited file will find the wrong offset and the reader will probably crash. Therefore, many programs remove the MakerNotes from the EXIF segment.
I am sure, however, that Adobe knows all the internals of any MakerNotes. Therefore, I am not surprised that you could read the EXIF data of the modified image. Don't expect this to be true for an arbitrary other program.
Changing the creation date and gps coordinates, I think, is not critical because these data blocks have a fixed size and will not modify any data offsets. The author tag, however, is critical because of its variable length (at least for fpexif).