expressions - Confirmation, kindly, please. Phrase "Is this sinking in"?

I appreciate your moderate and attentive treatment to the OPs as always.

A TOEFL textbooks give me this kind of sentence. ( Though in my opinion, since it is in the listening practice section, it sounds a bit abrupt. )

The whole practice is talking about the gene therapies.

Exerpt

At this point of time, there are three types of gene therapy. The first one entails leaving the mutated genes alone, but placing normal genes inside a cell and activating them. The second type involves stopping gene abnormality by binding a specific gene sequence to the abnormal gene sequence. The final type is a so-called gene operation, as it involves away a particular portion of DNA. Lastly, I'd like to explain the risk involving in gene therapy. As a matter of fact, it is no simple task to manually place a gene inside a deceased cell from the outside. For this reason, it is necessary to weigh the risk of side effects during and after treatment, is this sinking in?

Now, here, please confirm, the last phrase will drop on the definition of the below by Merriam Unabridged.

Assuming, the narrator is confirming the listeners if the recognition of the risks entailed by the gene treatment are enough absorbed by the listeners' minds. Am I correct here?

Thank you for your always moderate supports.

Answer

sink in TFD idiom

2. Fig. [for knowledge] to be understood.

Yes you are correct:

The narrator is confirming that the listeners are absorbing the information concerning gene therapy.