Having worked with hundreds of companies on their OKRs at Weekdone, I've seen many hack OKRs on individual level and use them "wrong" by having the KRs as milestones, tasks and projects. Yes, absolutely illegal by some leading OKR consultants and thinkers. But works like magic to keep goals in front of people.

Having the choice of having a developer or designer a visionary KR of improving x or y by z% vs getting a project, milestone or task done, in many cases the latter keeps them focused vs them rolling their ideas on the % KR.