> Line 154 only modifies the "basePath" and "baseUrl", which is fine.

Exactly! It modifies "baseUrl', which is used by "AssetConverter::convert()" to recompose file name.
Here is program flow:
1) "AssetBundle" line 154: baseUrl is filled by asset hash, like "adefce"
2) "AssetBundle"  line 160: file name is modified by "AssetConverter"
3) "AssetConverter" line 60: new asset file name is composed as "baseUrl" + "originFileName", so "jquery.min.js" becomes "/adefce/jquery.min.js".