I think buying a "foreclosure" unit from the developer is basically the same thing as buying a unit from the developer that has never been sold before. Just because the unit has never been sold before, of course, does not mean the unit has never been used. Of course it has been used - very frequently. In Hilton Head, it's probably been used every week since the place was built. An unsold unit is probably used as frequently as any other unit. A "foreclosure" unit just means the developer obtained it back and is selling it again. When I went to a timeshare presentation last year (didn't buy THAT time) and ended up telling them I wasn't interested, they then offered me a "better deal" on a "foreclosure" unit. I think they were trying to give the impression that it would be a good deal, similar to buying a foreclosed, abandoned house. The price was lower, of course, because I was indicating no interest until then, but the "foreclosed" unit probably was identical to the units they had already tried to sell me. Maybe in a different building or a different floor, but all the units are the same at this resort. This was Grandview - the same place where the OP bought his "foreclosed" unit and then had the wisdom to rescind the deal.
I tracked the deed history of a specific unit in Hilton Head I am interested in. The county recorder there has a web site where you can look up all filed deeds, and the deeds contain the actual prices that people paid to the developer. (The developer is probably hoping that people never stumble across that web site because the prices for the same things are all over the board - I guess some people do not hold out for the best deal they can get.) For this particular unit, a couple bought from the developer in 2003 for $12,500 (3 BR triennial unit at a Gold Crown resort), which I am assuming was the first sale for this property. (I'm assuming that because of the timing with respect to when the resort was built and because I could find no prior deeds for the unit). Apparently they failed to pay their maintenance fees (all the gory details are in a filed notice of lien, notice of auction, etc.). The unit went up for auction in 2010, and the developer "won" the auction and title was transferred back to the developer. The next deed for this unit is in 2014 from the developer to another buyer for $16,300. This buyer paid approximately the same amount as other buyers paid around the same general time (although, again, the prices are all over the board). The developer more than made up for the unpaid maintenance fees (many, many times over). They are still selling units at this place, and unless to try to track the deed history, there is no way of knowing whether you are buying a "new" unit (which has been used all along of course since 2003) or a "foreclosed" unit (which also has been used the same way).
Bottom line is that it makes no difference whether it is a "foreclosed" unit or a "new" unit. There is also no way of knowing (unless you do a deed search) whether the developer is selling someone a "foreclosed" unit to begin with (without telling them of course) and then trots out another unit (saying it is a good deal because they "foreclosed" on it).
The real bottom line, of course, as we all know (knew too late in my case), is that there is no such thing as a good deal when buying for a developer, whether it is a "new" unit or a "foreclosed" unit.