Unless you have a broken (or rare M-only syncing) shutter, that will work perfectly fine.
Prefiring sync for flash bulbs was a very transitory development. It came too late before electronic flash, timed bulbs could not compete with plain long-burning flash bulbs in power, and there was rather a mess of competing timings, so that basic delay-less X sync (as used by electronic flashes nowadays, and in B or long time setting with untimed bulbs back then) never got replaced. On all shutters I am aware of, delay flash triggers (M/F) are only present as a switch option besides X, if at all.
However, purely X-sync shutters were sometimes modified in the peak years of M and F bulbs, to make them more bulb compatible - if you have such a beast, you'd have to get it readjusted to normal operation.
As Graflex advocated solenoid triggering (where the delaying is at flash side), the likelyhood of encountering M/F modified or capable shutters on a Speed is rather low, at any rate unless it was for European export, where direct M/F triggers were more common.
Sevo