The answer is no, and I'll tell you why. A technician's job is to
repair machines that are broken, not to do cleaning, especially with a
periodic checkover, the scope of which never includes cleaning. If
the outer tub was so dirty, the technician should have given you an
estimate to replace it. So, if you feel that you didn't receive value
for the amount you paid, you should just ask for your money back. Is
the debris impacting the performance of your machine? Most washers
have some sort of buildup somewhere that doesn't impact performance.
If your answer is no, then why be concerned?

Maybe your biggest problem is that you listened too much to the person
who set up that service order for you, and really should have asked
the opinion of the tech himself when he was there working on his
dryer. If you said "do you think that this is money well spent and
that it offers good value?" he would have answered "no, save your
money, it achieves very little and your washer will work no better."
But since you didn't ask the question, he didn't volunteer the
answer. That isn't his job either.