Earlier quoted context omitted.
What objective measurements are good for engineering? You can come up with superficial ones: lines of code written, tickets closed, hours seen in office, but I doubt those are strongly associated with effectiveness. Everyone in has probably had weeks where they “did nothing” because they were working on a tricky problem or doing work outside of what was quantified.
Don't confuse objective with easily quantified. Did they ship the features they were responsible for? Did those features turn out well, with a low defect rate? Did they promptly address bugs? Any manager paying attention can answer these questions pretty objectively.
Is the objective measure of “well” a low defect rate? Because it sounds like you’re leaving a substantial amount of the value of an experienced employee on the table if your measure is “does it do exactly what we asked for it to do” rather than “does it solve our problems”.