The new Singleton 1.1 standard removed Truths because it was originally an optimization, but was causing headaches (you’re supposed to be able to pass in an arbitrary inner puzzle). You can find the link here.
This is going to be the new standard for everything except PlotNFTs going forward (although it is still in development) and it has support for hinting/memos as well as a few optimizations that make it about 15% less expensive.