If you have a copy of Madis Winchester book handy,
go to page 600. (Mines the 1985 edition)

There are sling swivel options pictured for Carbines using the lower bbl band.
Both a standard swivel and a 'Hook Eye' .
Some were a screw stud and riveted attachment. Others brazed.
I've never seen one that I thought was welded, but never say never.
A riveting job can be nearly seamless if done with the proper set up.

There's even the Hook/Sling Eye w/Stud alone. Which seems to be offered as a separate part to be installed by your favorite gunsmith or the owner.

I think the applications in the pics (stating 'for any rifle or carbine') might be refering to pre-WW2 mfg'g times.
But very early after WW2 when things started getting rolling again at W,
I wouldn't doubt that parts left over and demands/requests being made by customers would get you just about anything you wanted.
Just like it did Pre-WW2.