The BIG TESTER, would be a carbon pile load tester, you cannot complete a proper load test with just a MM.. or volt meter.
To do a parasitic draw test requires an amp meter or AmpClamp.
First off, I'll readily concede that I'm just a DIYer, and that you're a pro having far more knowledge and skill than I do. However, I'll also say that I've done both load and parasitic draw tests successfully using only a MM. (successfully, meaning problems were diagnosed by the testing). So, although the advanced tools almost certainly will do a superior job, I can't go along with the idea that it's not possible for a MM to produce reasonably accurate and useful results. Just my humble, non-professional opinion, based on personal experience. In addition, there are numerous sources online which describe using a MM for both of those tests.
And beyond that, the main point of my post was to offer the opinion that the prior efforts of throwing on batteries and an alt were just part-hanging, and that the actual issue had not been properly diagnosed. Based on the post, I did not believe this person is a DIYer, which is why I recommended another shop. I was trying to poke a bit of fun by writing big tester, mainly because of their failure to identify and fix the actual problem, regardless of what tools they were using.
The net is that it's disappointing to see you single out part of what I wrote as being wrong, without at least agreeing that the work done to this vehicle had been sub-par, and for them to go elsewhere. Or, if you don't agree with that either, then suggest a different course of action. IMO the idea is to help people, and I don't see how your post could help resolve their problem. If you feel that I'm all wet on this, then I guess we'll just carry on.