Some files are missing when doing glob

I have this code:

              const searchPattern = '{post,page}/**/*.{md}'
              glob(searchPattern, {
                cwd: content,
                absolute: true
              })
                .then(files => {
                  console.log(files.length)
                  callback(null, files)
                })
                .catch(err => callback(err))

And I would expect the files for {post,page}/**/*.{md} = {post}/**/*.{md} + {page}/**/*.{md}, but it's not in my case.

I have 2 files for {page}/**/*.{md}, and 53 files for {post}/**/*.{md}, but only 33 for {post,page}/**/*.{md}. Am I doing something wrong here? The searchPattern just works fine under node-glob, fast-glob.