That's to seal the strainer/drain to sink. There should be large nut that actually compresses the bedding compound (a/k/a putty). That's not the issue.

The sink needs to be held in place by something (RTV silicone sealant might do that) so that the sink doesn't shift in the opening. There are some clips that come with sinks that are either domestic SS or marine oriented (Grohe, Scanvik, or Kohler [for that matter]). I like the clips, but I guess you could depend on gooh -- but you need to make sure that it's really adhered well. It's better to use clips to hold it there and "gooh" only to seal it. If you ever need to remove it, it's going to be a mess to get out and will be difficult to rebed if you don't mess-up the countertop when you remove it.

You want the hose between the sink and the throughhull to have some "give" -- plastic and rubber expand and contract as you pore cold and hotwater through them. You really don't want to be working that thru-hulls in tension or comression. They should just be doing their job of sealing things. LEAVE A LITTLE CURVE IN THE LINE TO ALLOW FOR MOVEMENT, if you can.