Thats very true,

after changing the group in /etc/passwd
all the files hence forth created will have the current group
and not the older ones

Assumed when group is changed for a user the home directory of the user which in turns contain an unique inode, would change its group name based on the group id identified from the file.

Wouldn't the contents of the inode(group name) be refreshed with the current one?
Would appreciate very much if somebody explains at the level of inodes?

Thanks,
Mad