User Error. I didn’t notice that BuildAssetBundle now has an argument to it for BuildTarget. Nevermind. I’ll leave my error here for posterity.
This might be expected behavior, but I couldn’t find anything about it. It seems that if I’m working on an iOS project and I need to make an AssetBundle, the first thing that Unity does is switch me back to the PC platform, reimport ALL assets, then make the assetbundle for me. Then I need to switch back to iOS, which reimports all assets again, and then finally I get to make a build. Is this normal?