The mistakes children make in learning to

The mistakes children make in learning to speak tell linguists more about how children learn language than the correct forms they use.
What is the meaning of the bold part?

tell linguists more / about how children pick up and learn language / than (it tells linguists about) the correct forms of language used by the child.

Does the red it refer ''the mistakes"?
if it does then we can say it can refer a plural subject. correct?
if it doesn’t then I still fail to sense the sense of the sentence.
Could you please explain it to me again if it doesn’t?

Is this sentence correct?

It would probably benefit from the addition of a comma before ‘than’.

The mistakes children make in learning to speak tell linguists more about how children learn language than do the correct forms they use.
Now what?

That has changed the meaning. Now it is comparing the mistakes with the correct forms. This is possibly the original intention. It would make more sense than the alternative which I explained earlier.

It’s saying that when children make mistakes with grammar, that shows linguists more about the learning process than when children use correct forms (which they may simply be repeating without an understanding). I.e. if a child comes to you and says “I eated a worm”, it shows that they understand the concept of “-ed” being the standard past simple ending, whereas if they say “I ate a worm”, you don’t know if they understand the irregular form, or if they just learned that you use ‘ate’ in that context.

So, maybe it would be clearer as “The mistakes children make in learning to speak tell linguists more about how children learn language than when they use the correct forms.”

This scenario tells us more about the case than that scenario.

Is the sentence correct?

It’s unclear as to the meaning.

So what is your suggestion for clear meaning to this sentence?

Hi SC,

This means this description of a situation is better than that description.

Alan