What I'm curious is though, from an OEC or from a TE, why the need to interpret Genesis in this fashion?
The OEC has exactly the same motivation as the YEC.
They both wish that the facts were in agreement with the Bible.
But they have different ways of approaching the problem that the facts flatly contradict the Bible.
The YEC denies the plain facts, and the OEC denies the plain meaning of the Bible.
To an outsider, both methods seem equally ridiculous.