The VFR that was going up above 5000ft would make a broadcast on the Area freq before getting to 5000ft. Similarly, descending below (into the "potential" Multicom area) they would broadcast on 126.7 before they got there.
There are many Broadcast Areas (Mega CTAFs) where the frequency split at 5000ft occurs, and arguably, the same thing happens at normal CTAFs today: broadcast on the CTAF before you "enter" and broadcast on the Area during departure before getting too far away from the airport.
Exactly!
Geez guys - its not rocket science .......