No. We know this because neutrino (flavor) oscillations exist. An antineutrino that was created together with an electron, e.g. in nuclear beta decay, can be absorbed in a reaction that produces a muon.
My interpretation of the mathematics is that if you could select a neutrino with a particular mass by measuring the electron energy precisely in the decay that V50 describes, then that neutrino would be a mixture of e, μ and τ neutrino states, at least from the moment that you measure the electron energy.
Furthermore, it would be a non-oscillating mixture because it would be a pure mass state. The probabilities of getting an e, μ or τ when the neutrino interacts, would be constant, and not vary with position or time as with neutrino oscillations.