>>It's not really an open bidding process if you only evaluate one of 4 submitted bids.
Of course it can be. Depends what is meant by "evaluate." I've been involved with a number of RFPs where bids had to be ejected from the process, often regrettably.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1