Hi,
You may be misinterpreting the meaning from that sentence.
The ISP Config, does affect the search if the 4th flag is set incorrectly. So, if this is set as Unicast, then only freeview / on demand items are indexed, no IP channels, Sky etc. If the flag is set to Multicast then the IP channels and content is included. When you run a software update, this will also check your entitlements and set the flag accordingly, 0 for unicast or 1 for multicast. As your config is 1501021 , the correct flag is set to 1 in your case.
The config number itself however has no reflection on the actual software that is downloaded to your box, and we customise the software in house for talktalk boxes specifically.
Thanks
Karl.