We already did.
Article 30.2.C.2: “When necessary or desirable, a substitute,
rural carrier associate, or rural carrier relief employee
who is assigned to one route may be utilized on up to three routes. However, the employee’s prime responsibility is to the assigned route.”
Article 30.2.D.1: “A leave replacement assignment list showing the primary leave replacements
assigned to each route and the
second and third leave replacements to be utilized on each route…”
Article 30.2.D.3: “If the second and third leave replacements
designated for the route are unavailable, … the route shall be
assigned to qualified substitutes,
rural carrier associates, or rural carrier relief employees assigned to that delivery unit in the order of the longest period of continuous service …”
The ONLY parts of Articles C & D that speak to PTFs is that they may be assigned as Primary on more than one route & that they may be utilized on any route prior to using the Secondary & Tertiary subs.
@Twingrlie is correct that you would lose in a grievance using your arguments. You have been proven wrong time & again but refuse to concede.