Well, I always found it kind of neat feature in SCC and FC before it. It's not a big deal--just something that made me smile. It's as if the game was saying, not every shift and gear change is going to be done with laser precision. (You'll notice the cars in the GAME that have semi-automatic transmissions don't suffer this problem.) So it makes the older cars, especially the 50s/60s era cars feel much more organic in comparison.
In this sense, I wish SCC had a working clutch where you could take a much more active roll in the gear change process. It's one thing that I really DID like about Shift--clutch support is pretty good. Where as clutch support in GT5P is just awful. Get the timing right and it's fine. Get the timing just a little wrong and instead of a little grinding or clutch slip, you hear that "BA-BA-BA-BA-BA-BA" as you hit the rev limiter and you're then forced to go back to neutral again before shifting. It was so ridiculous that it took all the enjoyment of the G25/G27's clutch away from Prologue. And of course without using the clutch in Prologue, every single shift is always cracked off with laser like precision. So I think SCC is, in that sense, a bit more realistic. But it falls short because you really have no control over it.