If someone asks why you're doing something, that isn't bad. It's good to have some concept of what you're doing, and why. What problem are you trying to solve and how will this solve it?
If you can't answer – if you can't say any reasons for what you're doing – prima facie there is a criticism there. Why don't you know in words what's going on? Why are you choosing to do it?
This is not unanswerable. But you should have an answer. If you can't say any reasons for what you're doing and you also don't have an answer to why you're doing it anyway (to address the kinda default well known criticism that knowing what problem you're trying to solve and how this will solve it is generally a pretty good idea), then that's bad. You should either have a reason you can say, or a reason to do it without a reason you can say.
If you can't say a reason to do it without a reason which you can say, what about a reason for doing it without that? Whatever you don't have, you could have a reason for doing it despite not having that.
The point is, you ought to be able to say something of some sort. If you can't, there is a criticism – that you have no idea what you're doing. (If you can argue against that – if you do have some idea what you're doing – then you could have said that info in the first place when questioned.)
I'm not convinced the quotes are substantively justificationist. And I'm really not convinced by like, "Don't ask reasons for doing stuff, only point out criticisms." Doing stuff for no reason is a criticism. In general people ought to do stuff to solve problems, and have some concept of how doing this will solve a problem they want to solve. If they aren't doing that, that isn't necessarily bad but they should have some idea of why it makes sense to do something else in this case.
You can't even criticize stuff in the usual way if you don't know what their goal is. You normally criticize stuff by whether it solves the problem it's aiming to. But if you don't know what they are aiming for, then you can't criticize in the normal way of pointing out a difference between the results you think they'll get and the results they are aiming for.
And if they can tell you a goal, or a problem they want to solve, then they do have a reason for doing it. They are doing it to accomplish that goal / solve that problem.