That B-body illustration shows both a proportioning valve and a metering valve. The latter was never used on factory a-bodies.
Do you understand now? They are both combination valves. They appear to be the same. The application information is not quite correct with respect to dates of use. Don't believe me 'cause I typed it here. Go read what Chrysler printed in 1970.
Please go read Chrysler's introduction to Dual Hydraulic Brake systems.
1967 Imperial & Chrysler Dual Hydraulic Brake Repair Book - Session 232
and then at least this section about the proportioning valve
1967 Chrysler Imperial Disc Brake System From the Master Technicians Service Conference Session 233[/QUOTE
Sorry did not see that metering valve and only noticed the distribution valve and “hold off proportioning valve”
you are correct!