I don't think the article gives much of an impression on how SPy is on that front.

[0] https://www.modular.com/mojo

I remember chatting with one of the creators of PyPy (not the author of TFA) a number of years ago at HPI. He had just given a talk about how RPython was used in PyPy development, and I was fascinated.

To me, it seemed completely obvious that RPython itself seemed like a really interesting standalone language, but he would have none of it.

Whenever I suggested that RPython might have advantages over PyPy he insisted that PyPy was better and, more strangely, just as fast. Which was sort of puzzling, because the reason given for RPython was speed. When I then suggested that they could (after bootstrap) just use PyPy without the need for RPython, he insisted that PyPy was too slow for that to be feasible.

The fact that both of these statements could not really be true at the same time did not register.