Some people say yes, it is, IF the child is the one who chooses to learn that way.
I think it depends.
It depends on WHY those are the choices the child makes.
The short version is this: if the child chooses those methods because they don't really know of or trust other methods, it may not be unschooling. If they choose them because they think they are supposed to study those subjects, as subjects, it may not be unschooling.
The long version is… longer. :-)
In a world where there was no compulsory schooling, it wouldn't matter.
For some people, that IS the world they live in.
My own kids, for example, never started school, to be withdrawn because of some problem with it.
When they reached what typically would have be considered "school age," we continued learning the ways they had their whole lives. There was neither a switch TO curriculum, or a switch FROM curriculum.
It helped, tremendously, that my own education was non-standard. This meant that I had complete trust that we were fine, learning every day, through whatever we were doing, because I had experienced that kind of learning as a child myself.
We never "did math."
I didn't teach them to read.
We didn't do "unit studies." We never studied science, or history, or any other subject, as such.
We didn't follow any sort of prearranged plan, or curriculum.
The importance of this is not that those things are, in and of themselves, bad.
It is that my kids didn't learn to view the world as a set of "subjects," and specifically, did not learn to view learning itself as a matter of studying a subject.
For them, learning has always been interconnected, everything part of and leading to everything else, and focused not on a "subject," but on things they wanted or needed to do or to know. We all learned many, many things that could be mapped to the school subjects, if we wanted to describe them that way, but we didn't. It was not necessary to do so, except for on state paperwork, which the kids didn't have anything to do with.
For them to, at times, choose to take a class, or to use a textbook to guide their own learning, is no big deal. It's one of many resources they might use to learn, equally valuable as any other way. For what it's worth, they largely did not choose to do so until adulthood, when two of them wanted to do something that required specific training.
But if a child has been to school, and has learned to see life and learning the ways schools present it- as separate subjects, largely without context- and, especially, if their parents have had a typical education, and see learning the same way, then things are very, very different.
For a person with that background and environment, choosing- or defaulting to- classes or workbooks may make it very difficult and unlikely that they will ever transition to an unschooling way of seeing learning and life, as completely interconnected. As long as they see learning broken up into subjects, they aren't unschooling.
THAT is why, when newbies mention using such things, and that "it's still unschooling because it's what my child chose to do," people who have been around a while often remind people that such things are not necessary. The issue is not with the THINGS, it is with the conditioning that has already occurred, often unrecognized because it is SO prevalent in the dominant culture. It matters, a LOT, what their mindset is when they make that choice, what understanding of learning they are making it FROM. Just because someone asks for certain resources does not mean that they are really actively choosing them out of an understanding of what resources would be most appropriate. It might well be that they simply don't know any other way, or that they assume that these are the ways in which people learn. It is, after all, the most common way that young people in the dominant culture study things, and such things are easily available, and constantly promoted.