- Browsing HN, and your scroll gesture happens to start where a link is? Before you know it, you’ve navigated away.
- Long pressing to delete an app, and the app opens in the meantime? Awkward UX.
In the majority of cases, press gestures are competing with other gestures like scrolling. Waiting until you’ve released is often the first moment that it’s 100% clear which gesture you intended. If both gestures get invoked, it will probably lead to much worse problems.
I’m sure there are cases where act on press makes sense, but I don’t think it’s as dramatic as the tweet makes out.