smbmnt user needs to own the mountpoint if you want to mount rw

I just found out that it’s impossible on my system to mount /mnt/smb-docs as user bigsmoke, even with the following fstab:

//server/shared\040documents       /mnt/smb-docs smbfs   noauto,user,uid=bigsmoke,username=secret,password=alsosecret  0 0

I tried to chmod 775 /mnt/smb-docs; chgrp bigsmoke /mnt/smb-docs, but no luck. I had to actually chown bigsmoke /mnt/smb-docs. Does someone understand why? I noticed that I’m not the only one who noticed this.