This is amazing. Imagine being able to try apps on a website without installing them. Or make web apps with a sane framework in a sane language.
Android already has Instant Apps. It's a bit of work, but it doesn't seem super popular, and definitely less work than a Flutter rewrite.
Q: Why do so many Google Labs projects fail? A: Because Google gives them names that are common dictionary words, and their users cannot collaborate properly outside of official discussion channels because they cannot use a search engine to find answers to simple questions, tutorials and independent sources. Perhaps the greatest 'duh-hickey' of modern times. Thanks for asking why, Google... send me a check now.