Your assumptions are not unreasonable but have more margin of error than you might think.
First, if he was told it's a Sweet Sixteen from 1932 it was misrepresented. The Sweet sixteen was not introduced until 1937. Based on this fact alone I can whole heartedly agree with your point that pre war Sweets are pretty darned rare as compared to Standard Sixteens.
But on the other issues there is still room for it to be a Sweet, that safety was around till late 1951. And the "solid" rib (actually known as "raised, hollow, matted) was produced through 1961.
Let's hope your friend comes though with the numbers and we can give him some good news. And hey, even if it's a Standard some of them are really nice. That straight stocked gun ('23 standard 16)in the pic in my earlier post only weighs 2 oz more than my '51 Sweet Sixteen and it has a 2" longer barrel.
