The point he's making is the technology foundation can be built for the wrong product or the wrong market. After 2 full product reconfigurations or pivots requiring a TON of code being dumped you will wish you didn't have the overhead of building infrastructure with the first product in mind. In the end, the base reasoning for the foundations being built the way they didn't hold up in production.

Building something quickly that can be broken up over time is the best way to an MVP, and you can deal with scalability issues when you HAVE scalability issues. I consider scalability to be a good problem to have, because by that time you have actual traction.

If you are a bigco with a big marketing budget in a field in which you already have experience and business then by all means scale to millions of users at day one. Don't take on the cost of it in a startup, because the problem is TRACTION not technology with regards to scaling.