For legs of <10mins in lengths, at speeds of 120kts, as long as you choose a decent waypoint, you can be considerably off heading and still not get lost. So it suffices for EFT.
Perhaps. But when applied to a 50 nm PPL Skill Test navigation leg at 90 KIAS, it simply isn't sufficiently accurate to achieve the required limits.
MDR drift calculation is a very necessary skill. But not for accurate ground speed calculation.
When we are in the business of minimising airspace busts, it is essential that all potential sources of pre-flight planning error are minimised, so that the only corrections needed in flight are for actual W/V change.
Leon Jabachjabicz, I concur!