No, it isn't an example of a nominative absolute phrase. It is an example of a parenthetical clause. You could remove the part of the sentence between the commas and it would still make sense:
- Most of them he rejected out of hand.
The fact that they are 'too outlandish' is presented as additional information which is not necessary to the sentence.
A nominative absolute phrase is a non-finite clause (not phrase) that contains a subject and functions as a supplementary adjunct, for example:
- Most of them being too outlandish, he rejected many out of hand.