Yes, I pointed that out too: “many respondents use multiple OSes”.
But SO releases the data as CSV after a while, and depending on how they anonymize it the “N users ticked Windows+Ubuntu+Arch+Android” info might sill be available and convertible into “N users ticked Windows+Linux+Android”.
LemmyRS’s version is not even 2 months old (0.17.4, 2023-06-13), I wouldn’t worry yet.