A x-wind component of 0.2 Vso is the minimum that must be demonstrated, as has already been stated in this thread.
You seem to be suggesting that that is the certification basis for every aircraft ever certified, from Tiger Moth to A380.
As has already been stated in this thread, I do laugh at those who seem to be suggesting that the certification basis for aircraft that have been around for decades is ascertainable against contemporary test guidance. And even aircraft that are subject to a 0.2 Vso X-wind demonstration requirement are not thereby "limited" to a X-wind component of 0.2 Vso. The OP's question was about limits.
PS: I found this commentary by an experienced instructor to be informed by practical reality:
The "Demonstrated Crosswind" is a meaningless certification requirement indicating that on the day the aircraft was FAA certified that was the maximum wind available. ...
Aircraft that are certified under FAR Part 23.233 requires the aircraft to be safe for operations in 90-degree winds up to 0.2 Vso. Vso is the slowest speed an aircraft is controllable in landing configuration, at approach speed, no brakes and no special pilot skills. For a 60-knot speed with the C-150 this equates at 12 kts. These are minimums. This means that anything beyond a 12-kt. 90-degree crosswind exceeds the design expectations for an average pilot. If during the certification trials of a given aircraft, only ten-knot winds were available then that is the limit of the demonstrated crosswind component. This does not appear to be a very realistic criteria.
I found this article interesting as well:
https://www.flightglobal.com/news/ar...limits-419872/. In particular, these comments from the manufacturer of ATR:
ATR points out, however, that the airframer does not define the crosswind limit because it is not part of the certification.
Although the operating manual features demonstrated values, ATR states: “Typically operators define their own crosswind limits and incorporate those within their standard operating procedures."