I think you misunderstood this. tsx in this context is/was a way to run typescript files locally without doing tsc yourself first, ie make them run like a script. You can just use Node now, but for a long time it couldn’t natively run typescript files.
The only limitation I run into using Node natively is you need to do import types as type imports, which I doubt would be an issue in practice for agents.
I wouldn't call it running TS natively - what they're doing is either using an external tool, or just stripping types, so several things, like most notably enums, don't work by default.
I mean, that's more than enough for my use cases and I'm happy that the feature exists, but I don't think we'll ever see a native TypeScript engine. Would have been cool, though, considering JS engines define their own internal types anyway.
Similarly: TypeScript, despite what Node people might want you to believe, is not part of the JavaScript language.
I've always used ts-node, so I forgot about tsx's existence, but still those are just tools used for convenience.
Nothing currently actually runs TypeScript natively and the blessed way was always to compile it to JS and run that.
In fact, the team has back pedaled into trying to make its own thing like in the early days.