The WWII Jeep was a split contract - 3 vendors, actually.
And it worked because the units were identical - a Ford motor would work in a WIllys unit, etc.
Tankers, OTOH, don’t lend themselves to mass production -so a split buy would be the very definition of
insanity.
Agreed...Think of the ongoing years of maintenance, not only parts but the training of personnel for two completely different aircraft. Very, very expensive!