I think most information systems now include a statement of the purpose of the information. In this case, though, there's not going to be an opportunity to opt out. If you want to come to Canada, you will have to provide this information—that's the way I would expect it.
You commented on plans to share the information. I have no knowledge of what the plans are. I can see that if we want to respect each other's eTA, ESTA, there may be some advantages to doing that, but I haven't thought that through.