Is this a thrust button and can it be removed?

I won't disagree with you. I wanted to keep my old style tapered bearing setup. Was lead down the garden path by Moser to use green bearings. The axles I provided could not be shortened and re-splined. If I have a hint of something going wrong, it's $500 for another set of axles that will accept the tapered bearings.

Have you seen Chris Birdsong’s video on green bearings?
He REALLY hates them.

Junkerup on YouTube.

Found it.