...(a) There is the risk of overuse injury, (b) Cramming a lot of practice time into one day will not give you the same rate of progress as the equivalent practice time spread over multiple days (even assuming that the OP is fit enough to sustain this level of physical activity)
Several hours of reasonably diverse exercise in a day would not normally give most people an overuse injury, unless you do EXACTLY the same thing over and over. The fact that the O.P. is talking about other sports implies they enjoy and are fairly serious about athletics, and in fact says he or she has been skating "seriously for a couple months" - and anyone like that typically does spend at least a few hours in a day, several days/week doing sports. In other words, I interpret "low commitment" to mean that the o.p. has other athletic interests, and will not specialize in figure skating - but may be quite serious about athletics in general.
That is only a moderate level of activity. In many sports, like hiking, or biking, climbing, or paddling, or even golf, you routinely spend an entire weekend (as a weekend warrior) doing approximately the same thing, and you often add in a few extended trips that take longer.
Classes involve a variety of different activities, which probably eliminates overuse. The coach's recommendations WERE structured in other ways as well. Different activities during different sessions. That also helps prevent overuse injuries.
When I was involved as a volunteer in a LTS program, we routinely told people they would have to skate several times / week to master the skills. It's completely normal. And we tried to connect one or two public skate sessions with the period of time in which the classes were being taught, so that the skaters could add a few hours of practice in the same day. The coach's recommendations were NOT extreme, nor is my suggestion of doing a few hours in a day, perhaps with rests between.
(c) There is the risk that the OP will be so tired and overwhelmed that the skating experience won't be fun, and then what would be the point?...
As a paddling coach once told me, you get out of any activity what you put into it. Fun often comes from mastering skills. If you do any complex activity once/week, for only an hour or so, you'll probably never master anything. And, in sports, if you don't get tired, you are missing the point. Tired from athletic activity feels good. If you don't get tired, you can't don't train yourself to be better, faster, and stronger. Tired IS one of the goals of any physical training program.
BTW, another way to manage time well is to mix several desired activities into one. I personally wouldn't do off-ice ballet, partly because my body isn't built that way, but partly because it wouldn't accomplish anything else I want. Social dance would be more fun for me - because it adds social interactions. Likewise for outdoor sports with fun groups of people. And if the o.p. is in school maybe there is a way to get credit for an athletic activity. PE credit and/or writing a research paper on it.
Anyway, that is my take on this. But you are free to disagree.
P.S. I admit I'm not certain which STAR assessments the o.p. is talking about.
I guess he/she is talking about the
Skate Canada STAR program, the equivalent of the U.S. LTS classes. Look at that syllabus. You aren't likely to master the skills in the Canadian STAR 3 program without spending a few hours / week, just as the students who didn't do that in the LTS program I volunteered with rarely passed BS 3. (BTW I suspect SkateCanada Star 3 is a higher level class than US BS 3. After all, Star 1 includes Edges, Turns, Field Moves, and Stroking - way beyond the fall, get up, march, glide and dip of US BS 1.) The coach was being very realistic about that.
The
USFSA STARS program is OFF-ICE training, that doesn't just apply to skating - it applies to other sports the o.p. might be interested in as well. It doesn't need to be done at a rink, but can be done other places the o.p. might go.