Yes, those writings were also free from financial motivation and less subject to the author's feeling the need to justify them than currently produced ones. However, notice that other thoughts also before there was a financial motivation militate against them rather strongly.

An analogy: if someone wants a pet and begins by thinking that they would be happier with a cat than a dog, and writes why, and then thinks about it more and decides that no, they'd be happier with a dog, and writes why, and then gets a dog, and writes why that was the best decision at the time with the evidence available, and in fact getting a dog was actually the best choice, the first two sets of writings are much more free from this bias than the last set. The last set is valuable because it was written with the most information available and after the most thought. The second set is more valuable than the first set in this way. The first set is in no similar way more valuable than the second set.

As an aside, that article is awful. Most glaringly, he said:

To Asimov, only three laws were necessary