Well, yes-but: I appreciate the perfective/imperfective (frequentative) aspects difference as any Slav will, but it is EXTREMELY annoying to study a language, especially so closely related, through English and be forced to jump, ineffectively (at least if this was just ordering preselected words; but typing on the phone?!), through the hoops of verbose incidentals of its own grammar.
Right now I was allowed either of "eats / is eating", and there are many more similar cases. Again, I can understand that specifically with verbs of motion it is (somewhat) more important to differentiate the aspects, but I can construct cases where the present-simple English form would be a perfectly legal even as a translation (how about describing a painting? "the sky is blue and on the left a man runs towards a woman"); so, to sum up, I can't see how allowing "I run" here would be harmful (I don't think there is any sentence with just "Ja biegam" without the "twice a week" bit set out explicitly, and anyway nobody dreams of demanding symmetrically "I'm running" for that.)
So as you mentioned, verbs of motion are different, the aspect here is crucial. With other verbs, both Present Simple and Present Continuous are equally correct.
Yes, the way that English works, we could imagine describing a painting or telling a story and then "a man runs" would work. But we do not go into this (relatively uncommon) interpretation. Why? Because then we'd lose any possibility of teaching the difference between different verbs of motion, between "biegać" and "biec" or "chodzić" and "iść". The confusion as to what means what would rise infinitely.