It really does depend on how they enter the data. If they have entered the census entries as a family fact and have a census reference then it should be identified for everyone in a family.
HOWEVER. There is only so much hand holding you can do and if people are actively ignoring entering data in their tree then there is absolutely nothing that can be done to drag them kicking and screaming into entering data into Lost Cousins. Its exactly the same for the people you referenced that have their data on paper printouts. There's nothing wrong with having data on paper but if their priority isn't to enter data into a computer then there's nothing that can be done to get them to enter data onto a website.
There is no magic bullet here. The solution I'm offering is for people who are active researchers and have recorded census reference information but haven't transcribed that info into Lost Cousins format.
For some people the ability to automate the process might just be the nudge they need to enter the reference into their tree, especially when with just a double click they can get to the record online. For some the process will highlight where they are missing data and will give them an incentive to find it. For others even if you were to offer free lifetime subscription to Ancestry and FindMyPast they aren't going to put their paper records into a computer. That's just the way it is.
Note make sure you don't confuse two separate things here.
- The data in a GEDCOM will show facts for individuals some of these may include census references and so even if the person hasn't recorded a census the reference is sufficient to work out the census they have been found on.
- The data on websites that have census info and shows other members of the household
There is no link between other data on the website about different individuals and and the data in someone's tree. FTAnalyzer will analyse the data in a GEDCOM file is doesn't then go off online looking up census records to see if other records exist. It can only do what the user instructs it to do and going off online to look up data is something the user needs to tell it to do. At present there is no way without the user first having logged in for the program to search any of the websites and even when it does that at present there is no way for it to tell that other records on the same page refer to other people in their tree. For that to happen the program would need the user's permission to access the internet - trawl through website links (which of course means the user has to have entered the census reference first) then find a record then compare it with other people in that family then guess if it's a match.
Then EVEN if it did ALL of that it would still then require the USER to enter the data into their own tree in a format THEY control. As I said before FTAnalyzer cannot and will not attempt to edit someone's data and add stuff to their tree. So even if it found other people in the household the user would need to decide to add data to their tree. Again it's a case of leading a horse to water but not being able to make it drink.
If the user doesn't enter the data I can't force them to do so. Sorry. I don't know how many other ways I can say that.