No you’re misunderstanding, that was never and is not how it works.
Up until this point, a group with at least 2 adults and 1 too short child approaches a line of a height restricted attraction together. They ask for a swap pass. CM at entrance gives a lanyard to be exchanged with CM later in the line for a pass similar to the old FP. Kid and non riding adult go do whatever, riding adult waits in either FP line or stand by and rides. The pass then allows up to 3 people to ride through the FP line again, with certain passes expiring at the end of the day, others at the end of the month.
In order to use the FP line to get the initial swap pass, practice in the parks up until very recently (and possibly still) was to only require the initial riders to hold a FP, allowing the remaining riders to FP something else in the meantime or use it somewhere later. This was a point of contention in this thread, as some don’t believe people should be using the extra FP at other attractions period, and some don’t believe they should be using these at other headliners where the family will receive another swap pass.
The digital system is rumoured to be placing a window on the time the pass can be used (an hour-ish) and requiring the entire party to hold a FP in order to receive a swap. It remains to be seen what actually is happening, especially with the FP.
Clear as mud? I think I got most of it.