Add .gsheets to Spotlight under spreadsheets
The reason that Google spreadsheets aren't classified by Spotlight as spreadsheets is that information is missing from the Info.plist file within the Google Drive application.

For example, in the Info.plist file within the Numbers application bundle Apple define their "numbers" document with the Document Content Type UTIs of com.apple.iwork.numbers.numbers. Then further down in the same plist that UTI is then further defined as "Conforms to" amongst other things public.spreadsheet. And this is why Spotlight classifies Numbers document as "Spreadsheets".





However in the Info.plist for Google Drive there is no Document Content Type UTIs for gsheet files at all, and therefore no "Conforms to" either. So Spotlight just treats it as "Other".



This is something that Google should really fix, and it should be relatively simple for them to do so.

In the meantime there is a possible (albeit slightly hacky) potential fix outlined towards the end of this answer to a question on superuser.com: OSX: assign extension to content kind