Metro’s elongated planning process has Draft EIR released for 1 year before LPA vote (see K Line Torrance and Hollywood extensions EIRs), take 2-3 years to finalize after LPA vote (3-4 years after Draft EIR release). Also, phasing projects (see ESFV, K North, Eastside E, A to Montclair).
If FTA/FHWA/any other federal agency is reviewing an EIR/EIS (they have to review anyway if it crosses any covered waterway or highway) then they aren't going to get comments in the allotted timeframe. If they have review responsibilities they are going to get delayed just by that.
That leaves a lot of time to find money for the shortened phase 1. Measure R/M directly provide about $3.6 billion (which would be increased for inflation). State/federal match would bring that up to a lot, if compared to how poorer performing Bay Area projects have done with grants.