Thanks for the replies WCH.
I don't own "J.R.R. Tolkien: A Descriptive Bibliography" and had just assumed, though based on certain descriptions, that this change showed up in Tolkien's lifetime.
And when I said I thought Tolkien was "mistaken" I only meant in the sense of creating an inconsistency between first and second editions -- especially after seeing WPP and knowing JRRT's seeming reason to change
Finrod (as the name of the Elf who stayed in Aman) had become a non issue . . .
. . . in other words, my choice of "mistake" is very much based on my approach to canon -- I favor the approach, even from JRRT himself I mean, that the tales of the First Age keep in step with already published text (what little there is of it concerning the First Age anyway, relatively speaking) -- unless an "internal inconsistency" is desired of course.
And while I like the alliteration in Finrod Felagund, I have no problem with Inglor Felagund too.
But as I've derailed the thread about canon, I'll shaddup now