In general, I think it is helpful in discussing work trials if people (including the OP) distinguished between three different things that are commonly called work trials:
Take-home trial tasks / timed online tests, which typically take somewhere in the region of 2-8 hours and are designed to be doable on a weekend or otherwise without work disruption.
Short (usually 1-3-day) work trials prior to receiving a job offer. This is what I usually think of as being referred to by the term “work trial”. While it’s technically true that these “interruption of regular employment to complete” (quote from OP) I think it’s generally pretty manageable to make this work by taking e.g. 1-2 days of vacation.
Long (often several months) “work trials” that essentially act as extended paid probation. I’ve seen these at a few EA orgs and sometimes feel iffy about them, but IMO they’re not all that different from standard probation practices in the US. They definitely require “those currently employed full-time [to] leave their existing job”, though.
I’m not sure which of these the OP was including in her claim. Presumably not the first one?
Thanks for clarifying, I agree category #3 is the most dicey of the three.
How do you see these trials as differing from standard probation? Is it that the chance of a no-hire at the end is higher? Or the length? Or something else?