Yes, this is the normal behavior.
Here’s how you can see this for yourself:
Create a brand new IS document type on 6.1. Then set publishable to TRUE.
You will see that the Broker doctype has the same wm:is prefix.
Are you just wondering why things look different, or is there another reason that you are concerned about this?
Regards
#webMethods#Integration-Server-and-ESB#Flow-and-Java-services