NO. That's the worst way to do almost anything on the Internet, and should be considered a last-line defense, if nothing else can be done. Here, it can be. See my comment above.

That's my whole question, do they do random audits, or is it the job of customers to double-check their results for possible attack or compute-theft and report.

It seems wrong to call it a "job of customers". It's like you wrote a Bitcoin client which didn't verified hashes of transactions, "trusting" everything. Or like serving a website with login feature supporting only HTTP, not HTTPS. It is a very basic feature of whatever software would connect to such services.

So it is the job of the customer to write their own Bitcoin or HTTPS client, in your metaphor.

Every technology was (very) underdeveloped at some early point in its evolution.

That's what I asked, how developed is it now. Why so defensive?

I don't know how developed is it now, I'm not associated with the startup shown in any way. It's mainly a question to them. However, in terms of wider industry, in general distributed high-performance GPU(-like) computing "for everyone" is in its infancy. 99% of what was already done up to this point was targeted to people who would both buy and supply power "in bulk", not "in retail". Perhaps with a little exception of several excellent projects like Folding@Home and other @home's.