You gotta quote the whole thing. "...(5)A long call pilot...(f)who is assigned a rest period....(2)via telephone contact...(b) if not contacted directly by Crew Scheduling, have such rest period begin no earlier than two hours following the first attempted contact. In such case, the pilot must inform the company within nine hours of first attempted contact if they are unable to begin their rest as scheduled."

So, per the bold part, contractually they cannot start your rest for 2 hours if you do no answer the phone. My reading of the second half of that clause means if they assign a PWA-compliant rest period, and the pilot is not able to begin such rest period, then they must contact the company within 9 hours of initial contact to tell them they could not start the rest at the two hour from initial contact point.

So, scheduling calls at 0800. Rest cannot start until 1000 if the pilot does not answer the phone. If for some reason the pilot could not start his rest at 1000 then he must call scheduling by 1700 to inform them of such. It doesn't specifically mention what a pilot should do if scheduling calls at 0800 and puts them into rest at 0830. I guess the PWA assumes that the company will follow the PWA. Assuming a pilot is on a contactable status at the time of initial contact, the safe play is to still abide by the 9 hour rule.

This exact scenario happened to me this year. Scheduling called me to assign me a rotation ~31 hours from report. I needed the 30 hour rest to be legal so in their voicemail they also put me into rest starting 15 minutes after the phone call, so not legal per 23.S.5.f.2.b. I called them right at 9 hours from their call to tell them, and they pulled the rotation and put me into a fresh 30 hour rest period right then.