They have a ton of second basemen. But I suggest you check and see how many of those have EVER played SS, let alone have credible experience there. And just because a second baseman played a few games there in the minors doesn’t make him a viable MLB SS. Organizations play prospects at the most valuable positions they can handle. For example, Nick Dunn has played a total of four innings at SS in five years as a pro. OPS is nice, but SS is the most important position on the infield and most difficult to play.
If they are committed to Edman in CF, they may need more at SS than Winn. I get why Fermin doesn’t impress, but they don’t have many other clear bench options.