That is a very workable approach, so long as you consistently study. For motivation, if you'd like to get better at mathematics just as a life goal, that should be valid enough to spend time on the hobby. If you're studying primarily for personal enjoyment and fulfilment (and especially if you find joy in the process of learning), the slower pace doesn't matter as there are no expectations to learn quickly.
If you're studying mathematics or a technical subject for work, I believe it's better to earn a graduate degree from an accredited program for the resume (as a record of passing proctored exams is seen by hiring managers as strong evidence of learning), plus it's nice to be able to learn from your fellow students and ask the professor questions.
For myself, I've found it much easier to find motivation to consistently self-study mathematics outside of accredited coursework by practicing out of personal interest, as it eases up a lot of pressure about learning a certain concept by a certain time. I won't expect to learn as quickly as the person's reported progress in the submitted article, but this also makes the practice more enjoyable and easier to keep up in the long term for myself.
One hour a day should be enough to make steady progress.
Setting aside 1-2 hours a day should be enough. I think this is not unreasonable for most people. But why? Unless you need it for a resume or degree, I don't think it matters that much. So you can make a blog post about it?