More likely, in that part of the spectrum, they were seeing adverse effects from (probably undisclosed) military R&D activities. Might as well have been sunspots, for all they could've done about it.
But other phenomena correlated with sunspots do cause UHF interference, so while wrong on the details I generally believe the story.
What would be some examples of such phenomena, bearing in mind that we're talking about very short-range wireless links in a band shared with primary military users?
It's not as if conflicts in that band haven't arisen before: http://www.w5yi.org/ama_news_article.php?id=191l
Another example: http://www.tdsupplies.com/articles/395_MHz_Military_Radio_Re...
The collapse of the magnetosphere on the night side following impact of a coronal mass ejection—which not only make a lot of VHF and UHF noise, they have enough power to just break a device.
On the surface of the Earth?
If that ever happens, you have much bigger problems than a malfunctioning garage door.
At 433 that's pretty close to the 432.1 band some of us use.
Its possible for sunspots to really mess with HF and lower VHF like the 50 MHz 6M band but way off for 432.
Sunspot correlation with sporadic E (bouncing off the ionosphere) is common up to 50 MHz and drops off rather fast. I've made hundreds, thousands of contacts on 6M sporadic E but precisely one in my entire ham radio career on 2M which is 144 mhz pretty far from 432.
What does mess with vaguely 2M and up including 432 is tropospheric ducting. Basically a weather front or extreme fog makes a poor waveguide out of itself. Its somewhat location dependent.
One 70 cm band specific problem that could affect 433 mhz unlicensed stuff in a local area might be (legal ham radio) experiments with wide band ATV using a channel that overlaps the unlicensed band. That has nothing to do with sunspots.