You are absolutely correct that the semi-hollow bodies have a block of wood under the strings while true hollow bodies do not. Basically, a hollow-bodied guitar is an archtop acoustic guitar with pickups. The semi-hollow design preserves the appearance of hollow-bodiedness while cutting down on the feedback that hollow-bodies are prone to. It also is less fragile. Most semi-hollow bodies also have laminated tops which cuts down on feedback even more. The classic semi-hollow bodied guitar is the Gibson ES-335 and most of the others on the market, including the Guild Starfire IV are copies of it. As far as f-holes go, the Gibson Lucille model that B.B. King plays is a modified ES-335 in which the f-holes have been eliminated. Probably for even more feedback control.

I'm sure that the SF4 designation on your guitar simply means Starfire IV. The "D" could mean "deluxe" or something.