No the passage states that in order to be a fiend something must be LE (absolutely is not mentioned at all in this context and it has already been established this is not the totality of their nature or essence and furthermore that even the same alignments allow for different ethos, philosophies, personalities and so on)... so I'm not sure where you're getting that they must be absolutely LE or even what that term means(since law and evil exists on 2 separate axis in the D&D cosmology) in regards to a platonic form or being absolutely evil or absolutely Lawful... since you can't be absolutely more than one thing... absolutely means in totality...