The “Seam Grip +WP” is the same product that used to be called “Seam Grip” and you’re right – I just checked and “polyurethane” doesn’t appear anywhere on the new tube or packaging.
Most of the content on this site was written before they changed their product names and messed everything up, so I’m going back to add “+WP” everywhere Seam Grip is mentioned to (hopefully) make this clear to everyon, but some shops still have stock of plain old “Seam Grip,” so we’ll see if this causes even more confusion.
I looked at some Seam Grip+SIL reviews online and it seems like you’re not the first person to make this mistake… I think an email to Gear Aid expressing your displeasure would not be uncalled for.
I used to not apply anything at all to the inside of the seams, so don’t worry too much about it. In your situation I would apply some Seam Grip+WP to the outside of the tube-to-tube-to-floor joints (those are the most likely places to leak), and you can decide if you want to apply it to the outside of all of the seams or just wait and see if it’s needed. I typically apply it to the outside of the seam strips on the underside of the packraft to protect them from abrasion, and if you let it cure clear it actually looks pretty good, so in your situation I might just go ahead and coat all of the seams on the outside so you don’t have to worry about leaks developing in the future.