Whenever you share a link on Seesaw that links to a Google Drive file (eg it says docs.google in the URL) Seesaw will 'helpfully' prompt you to 'Try Google Drive Integration', this is not usually very helpful IMHO.
Because choosing 'Go to Add file' means Seesaw will convert the original Google Doc (or Slide etc) into a PDF, which changes how it appears in the browser, and means any changes you make to the original doc will not be updated in your post.
This is fine if you want it to be a PDF, but not if you don't.*
My advice is to choose Continue, as long as you have made sure the original Google Drive file is shared 'anyone with the link ...' or Public.
I first saw Grade 4 teachers doing this, and as they've been doing it for a while now, I think it's safe to assume that it's working well. They use a Google Doc as this gives them much greater freedom in terms of formatting, adding images, using a table, adding inline links and so on, then they just share the link as shown above with parents. As it is a Google Doc, if they have to make a 'oops how did I miss that?' changes after they've sent out the link, to need to stress; any changes you make are dynamic, updated in real time.
Here's an example from Katie Seniors class: