No. I don't think there is a strict line between relaxed or eclectic homeschooling and unschooling. The difference comes from following a set curriculum more closely, being more directive, not letting child have much input, or taking seriously the child's interests or supporting them -- which is more often associated with (strict or authoritarian) homeschoolers.
I think the term unschooling can be - how you define it. For some, this may include relaxed or eclectic homeschooling. For others, it may mean something else. It doesn't necessarily mean that there are no rules, boundaries, or parameters though. It doesn't necessarily mean you're not authoritative or permissive.
There's also the term or expression radical unschoolers. This is referred to those who extend the concept of unschooling to other aspects of life -- letting the kids decide on bedtimes, mealtimes, what they eat, access to the computer/tv, etc. The parents here are often permissive or uninvolved and do not usually set demands/rules on their children, though they presumably do still expect table manners.
Perhaps a radical unschooler or someone with a stricter definition of unschooling or interpretation of it would disqualify a parent nurturing a child's interests, including algebra, with making online opportunities available. But do you care? And why get so hung up on it?
Another point is that what works is for 4-6-yr-olds or with eg/pg kids is likely to change over time, and often over the course of a very short time. Nothing is set is stone here. Everything is subject to change.
Algebra or higher math, in particular, is very difficult to teach without veering into more structured learning and that's just the nature of the beast, I think. But there's so many textbooks, videos, and online courses today that the world is your oyster.
