Here is the PWA verbiage. Notice it says online or offline and does not mention positive space seat on the second flight. Notice also that despite your commuter protections, you don't want to make a habit of missing your sign in.



A commuting pilot who travels to his base by air will not be eligible for treatment under Section 23 Y. 2. unless he has attempted to travel on at least two flights (on and/or off line) that: a. show adequate actual seat availability within 24 hours of the departure, considering
the pilot’s seniority and the normal load factor of the flight; or, on which the pilot has a jumpseat reservation, b. are scheduled to arrive at his base at a reasonable time before his scheduled report, and c. are separated by at least two hours.
4. It is expected that a pilot will avail himself of Section 23 Y. 2. on a rare basis.
5. A pilot who has demonstrated a pattern of inability to report as scheduled will be subject to progressive disciplinary action.