No, not an issue. My greencards also only had First name, middle initial and last name on the front. On the back they had first name, surname, one full middle name and only half of my second middle name. Never an issue.
In Sweden it's normal to have two middle names (often counted as first names, so I guess technically you have three first names and one last name), and the US isn't made for that many characters, lol. So every US document I had (from SSA, DMV etc), my second middle name was always only half, instead of "Therese" it was "The". 😆
So the first thing I did when filling out my N-400 form was to remove one of my middle names in the "do you want to change your name" field, so I would only have one middle name. It has made things sooooo much easier!