Yes, it is the cause. The problem is that the configuration script contains commands that refer to features not available (wireless) and bombs out.
It has happened before.
However it is not as critical as it sounds, at least not when you make small incremental upgrades. I.e. you upgraded from an earlier 6.47.x version.
In that case no conversion is really necessary and the fact that the script failed has no further effect on the operation of the upgraded router.
(I had this problem before and my router still works fine)
Of course it may/will be different when you make a big version jump and there actually may be things that need changing in the config.