all forms of disbelief/kufr amount to shirk in one form or another… think about it…
see the verses i posted earlier
in addition to TH’s correction of the translation… you can see that verse 5:83 says
“When they listen to that which hath been revealed unto the Messenger, thou seest their eyes overflow with tears because of their recognition of the Truth. They say: Our Lord, we believe”
so they believed in the revelation sent to Prophet Muhammad (saw)… they are certainly not mushriks