A similar editor was made for the book Thing Explainer[1] by Randal Munroe from XKCD. A book that explains all kinds of different things, from space shuttles to microwaves using the top 1000 common English words.
Indeed. I thought it was an interesting experiment. The results make it abundantly clear that 1,000 words are not enough to communicate about science and engineering topics effectively even at an introductory "plain English" level.
Some of the explanations are actually going into a textbook now, to accompany more traditional text. So it seems professionals disagree with you. I will concede that it might have been clearer with the top 2000 words or something, but that's my perspective and plenty of kids might disagree, especially those that have grown up with weird dialects or even sociolects like AAVE.
No. He's doing some drawings for text books. There is no chance that the thing explainer 1000 words affectation will be adopted for the text book for the purpose of actual teaching.
Just a small nit:
The words sound alike but they mean different things. You should have read everything, then you would have seen the reference.
Source: grammer.
[1] https://xkcd.com/thing-explainer/