why does this use LMMathItalic10-Regular for the OS numbering?

\startitemize[m,packed,text]
\item a
\item b
\stopitemize

\os clearly works in other parts because it's using minion

% pdffonts file.pdf          
name                                 type              emb sub uni object ID
------------------------------------ ----------------- --- --- --- ---------
TCLXBY+MinionPro-Capt-Identity-H     CID Type 0C       yes yes yes      5  0
JAHMWQ+MinionPro-Regular-Identity-H  CID Type 0C       yes yes yes      7  0
UGISSP+MinionPro-SemiboldDisp-Identity-H CID Type 0C       yes yes yes      9  0
LBRKWQ+MinionPro-SemiboldSubh-Identity-H CID Type 0C       yes yes yes     13  0
FVROKN+LMMathItalic10-Regular        Type 1C           yes yes yes     14  0
VQGIRJ+MinionPro-Semibold-Identity-H CID Type 0C       yes yes yes     16  0
TMNGMR+MinionPro-It-Identity-H       CID Type 0C       yes yes yes     18  0

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—Mohamed