What scares me is that they do OS wide change based of wording "This can make", "And since we suspect" and "In all likelyhood" instead of doing actual tests. I know that open systems doesn't have required workforce, but doing changes based on subjective reasoning is slippery slope.
They care about making OpenBSD secure, not about producing security exploits.
Many OpenBSD devs are security researchers in academia. If they hear whisphers over beers that there are new Spectre attacks coming that exploit this or that, they might not be able to reproduce the exploit without putting a lot of work into it (it's research after all), but they might be able to prevent it by making a simple change, like disabling hyperthreading.
OpenBSD cares more about security than basically any other trade-off in OS design (performance, usability, ...), so it makes sense to me that they went this way. If you want a balance of security and performance, OpenBSD is not for you any ways.
Did it scare you when your operating system started to support it, on the basis that it would "in all likelyhood" be fine?
For a system aiming at security, it's a completely valid choice to disable things that start to look questionable, even if it's not conclusively proven yet. Just like potential software vulnerabilities are patched even if nobody has demonstrated that they actually are exploitable yet.
