Discrepancies in Tolkien's writings

[Elentári_O_Most_Mighty_1]

I have been thinking about this and puzzling it over for a while...but I am still stuck. Once again, it is over the meaning of 'Legolas'. (Sorry, guys... ).
But I was wondering, because in LOTR Galadriel calls him 'Legolas Greenleaf', which could be taken to mean that 'Legolas' means 'Greenleaf' (rather like the Glittering Caves of Aglarond- where Aglarond means Glittering Caves I think).

In Tolkien's letters (211, to Rhona Beare), he says:

Legolas means 'green-leaves', a woodland name- dialectal form of pure Sindarin laegolas...

(Tolkien goes on to name the roots of the parts of the name, etc.) It is interesting that he says it means 'green-leaves' plural, not 'green-leaf'.

In the Book of Lost Tales I (under the entry in the Appendix for 'Tari Laisi') it says something completely different:

The following note is of great interest: 'Note Laigolas= green-leaf, becoming archaic because of final form becoming laib, gave Legolast i.e. keen-sight . But perhaps both were his names, as the Gnomes delighted to give to similar-sounding names of dissimilar meaning, as Laigolas Legolast, Túrin Turambar, etc. Legolas the ordinary form is a confusion of the two.'

This is a complete contradiction to what he has written elsewhere...

What are your thoughts on this?

Do you have any other examples we could puzzle over?