Technology

The Hubble is also in a rather low Earth orbit (340-ish miles), which enables it to use magnetic brakes which allow it to ditch the excess energy from its reaction wheels into the Earth's magnetic field so it can stop pivoting when it aims. The further away you get from the planet the less effective that becomes. The bigger your object is, the bigger your reaction mass needs to be.

And the Hubble doesn't inherently roast or blind innocent bystanders as it swings its point of aim across all of the intervening space between its targets. Maintaining a steady shine on one particular point on the surface is one thing, but these idiots seem to be implying that they will sell sunlight-as-a-service via some kind of subscription model to multiple customers, so they would presumably be changing targets all the time.

The Hubble can only rotate very slowly. Per the article, 90 degrees in about fifteen minutes. Its advantage is that it only looks at targets that are very far away and hold still relative to the Earth, so there is very little parallax to worry about. If you wanted to go faster you probably can't use the reaction wheel method that it does; you'd have to use thrusters which would consume finite fuel that'd eventually (or quickly) run out, and at that rate there's no way you could do it as accurately. For the Hubble specifically, the amount of time it takes to get on a target is broadly irrelevant, only that it can keep itself there once it eventually achieves targeting. This would not be so with the hypothetical solar reflectors, regardless of what altitude they were flown at. And low altitude orbits would be the worst, because they'd be flying over the target's head at tens of thousands of miles per hour in terms of ground speed and would have to rotate very quickly in order to remain even vaguely pointed in the right direction.