when you are talking about legalities and foreign governments, it is more complicated then married is married because it comes down to whether the US govt will accept the marriage document. On the other hand, they come to the US and get married, then married is married is clear and with an apostille, just about any first world country will accept married is married.
the US has to accept the marriage document, which can be complicated in and of itself
what the poster wants is to get the spouse into the US as fast as possible, enter on K-1 get married, its the same diff to the US govt as if you do a K-3 and bring them in that way.
the switch to the K-3 may make the process take even longer, which nobody wants