I'm always really skeptical about these giveaways, but in this case my guess is:
a) AIDA64 isn't the typical semi-finished junkware on these types of websites, so word will get around the tech communities more than usual
b) offering a slightly earlier version will let people who bought 2.20 to still feel good about their purchase, get more users and lead at least some people demoing 1.85 to upgrade sooner
Generally I hate when companies give away or deeply discount software that I already bought (Steam sale gah!), but in a case where we're talking industry-leading software with a much broader interest than realistic potential market (like most benchmarking suites) it's probably a good decision to make the software pro reviewers use somewhat accessible to the curious general tech hobbyist who reads the reviews.
So fair, it's disingenuous to say v1.85 is a $39.95 value, but for someone like me who couldn't really afford AIDA64 but has interest in benchmarking especially, it's forgiven.