hreflang is so surprisingly complex, in practice, I think that anything that makes it easier to understand and debug should be considered a requirement:).
hreflang kunjalo Akumangalisi eziyinkimbinkimbi, empeleni ngicabanga ukuthi yini eyenza kube lula ukuqonda futhi kokulungisa amaphutha okufanele ibhekwe njengelungelo imfuneko:).