bash expands {c,h} before the command sees it

gistfile1.txt

$ echo fish >a.c
$ grep -r --include=\*.{c,h} fish  .
./a.c:fish
$ grep -r --include=\*.{c,h} fish  .
./a.c:fish

grep doesn't like {c,h} 

$ grep -r --include="*.{c,h}" fish  .
$ grep -r --include="*.[ch]" fish  .
./a.c:fish

and look at number of args - 6 v 5
$ echo grep -r --include=\*.{c,h} fish  . | wc
      1       6      43
$ echo grep -r --include="*.{c,h}" fish  . | wc
      1       5      33

$ echo grep -r --include="*.{c,h}" fish  .
grep -r --include=*.{c,h} fish .
$ echo grep -r --include=\*.{c,h} fish  .
grep -r --include=*.c --include=*.h fish .