This is not the case. Fiancé and spousal visas take about the same to process, about 18-24 months. This is why I personally think that if you have to wait the same time anyway, might as well apply for spousal as that is a much better option - you get a GC right after entry to the US. With a K1, that’s just the beginning as you have to apply to adjust status and wait even more, not to mention the increase in fees that is taking place at some point in the near future.