I find that the $autoLoadConfig is 999 for both the init_ scripts. Setting colorbox to 998 and sitemap to 999 resolves the problem.
I note that the init_ installer scripts seem to have some commonality, but are not the same.

I think that this problem of different results due to different environments is maybe related to this autoloader issue:
https://github.com/zencart/zencart/issues/1228