In the tests in the article they tested only two HDDs compared to 15 SSDs and they subjected the HDDs to far fewer power loss tests and one of the HDDs failed, so problems with power faults are not limited to SSDs. It is possible that SSDs do not handle power problems as well as HDDs, but I saw nothing in that article to convince me of that.

I know from experience that HDDs are not immune to failure due to power problems. I was involved in a problem a few years ago where a data center was subjected to a power surge from the power company and experienced failures of 50 HDDs in high end SAN units.