I'd never make fun. It's just not a very effective thing to do is all. I'm not going to do anyone a service by giving them a pat of the back and a pass for making ineffective training decisions. I don't expect anyone to do that for me either
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They would be better off doing negatives.
The thing is for someone who has not done a lot of pullups it's really time to say "i'm weak at this portion or that portion". That's like doing bench for the first time, picking too heavy a weight, getting stuck at the bottom and saying "i'm weak off the chest". No, the weight was just too heavy. Same thing with pullups. Your bodyweight is just too heavy. I'm not saying that people can't be weak at certain portions of a pullup although it's not something I've ever thought about or heard discussed.
But I'm trying to make sense of this. Are you saying sense you were weak at the bottom you worked only the top? Or you just worked the bottom.
This all comes down to, as I've said many times, a preoccupation with certain amounts of reps, sets, and stuff like that. If you want to get stronger at a movement, then the first thing you need to let go of is the idea of this for size and that for strength. The best way to get better at pullups is to do pullups. Even if you can only do 1 rep for three sets. Because next time if you do, for instance, 2-1-1, that's and improvement. Developing strength is largely about training movements.
But most people have been sold this bill of goods about 3 sets of 8 or some other combination. And so they short change themselves at the beginning. I'm not saying that all sorts of things don't contribute to success at one particular movement. Because they do. But you start always with the movement.
Even a person who can't do one pullup can probably do a negative rep. And that will contribute to strength development a lot faster than a partial rep. And by the same token if you can't do a pullup it means you are weak, not necessarily broken. so getting on a machine designed for injured people is a little silly for a healthy able-bodied, but untrained individual. If you are simply too heavy to do one...well, we all know the cure for that.
By no means am I saying there aren't other ways to skin a cat, though. I'm a pullup freak and I can well attest that one great way to get better at pullups is to do them more often. But for that you need to stay well away from failure. You gradually increase the volume even if you are repeating basically the same sets. But this is a NEURAL device. I think it's called synaptic facilatation. It doesn't mean the answer is to do endless sets of lightweight pulldowns since then you are not training the same synaptic pathways. But it's a trick that's hard to pull off without interfering with the rest of you workouts and it would have to be done very slowly. The mistake people make is assuming that jsut because you stay away from failure there is not neural or other metabolic cost. And of course there always is to some extent.
If you were to replace one of those row exercises with pullups on lower one...but stopping short of failure even if that means your basically doing the same thing twice, you'd probably see some quicker progress on pullups. You could still go to failure (but not beyond) on upper two like you have been doing cuz that is at the end of your traning week and it's really the only thing you are working to failure on.