This was an interesting video. We're not in the market for a house so it isn't my issue, but for anyone considering buying a non stick-built house this would seem to matter a great deal. The very basic TLDR is that "manufactured" homes are built to a federal HUD standard that is lower than "modular" homes which have to be built to the same local code as a stick built house which is a much higher standard. And "manufactured" homes are all built on a chassis with wheels (which some manufactured home companies are trying to get permission to remove on site), whereas a modular home is built to be put on a foundation like a stick built home. The key is asking what building standard the house was built to.
https://www.youtube.com/watch?v=bRqPa_xGlIg