Overall I don't see Penpot being a realistic competitor to Figma, and I can't see this as being something that was done as a knee jerk reaction to Penpot's social success.
First, why it isn't a realistic competitor. While building everything out leveraging SVG as its main rendering engine allows for parity with code as an advantage, the inherent disadvantage it has is handling large files. For larger design teams, files often have thousands of designs and pages. Sketch has an advantage here over Figma primarily because it has a higher upper bound on possible memory that it can allocate to each file. Penpot not only has the memory restrictions Figma does (since it operates in the browser), it's also tied to the browser rendering performance of SVG, which simply wasn't designed for the scale designers operate at. It tends to get extremely slow once you have 50 or so pages in a single artboard. This means realistically, Penpot is competing for the casual design market, rather than the larger enterprise-scale design market. Figma's approach for this market has always been to use it as a top-of-funnel expansion opportunity, which is why their free tier targets these users. In general it's very hard to compete with something that is both industry-standard, and free. Penpot theoretically offers more functionality than the Figma free tier, but since it can't support the scale that Sketch/Figma does for larger files, it greatly narrows the market they're targeting. The market for users who want to build extremely advanced designs, but who also want to create extremely small files, is a narrow group.
Second, with regards to this being a knee-jerk reaction to Penpot's dev tooling, the dates just don't line up. Penpot really exploded in reaction to the Adobe acquisition announcement in late 2022, but Figma acquired a YC company known as Visly in 2021. Visly was apparently working on some design->code elements, which was really the first inkling that Figma was exploring this. It seems like this was being worked on / thought about long before Penpot took off. Given the submitter of this story appears to be Emil Sjölander, one of the Visly founders, I suspect that it's a fair assumption that Visly turned into Figma's Dev Mode feature: https://www.ycombinator.com/companies/visly