Rationalfrummie, I think checking for bugs has always been the halacha. What is new is detailed regulations about each vegetable — soak for 15 minutes in warm soapy water, etc — and bans on certain vegetables unless they’re frozen or hydroponic or whatever. As mentioned recently on Torah Musings, even today some halachic authorities (such as R’ Shlomo Amar) will say that the requirement is simply “wash produce and check for bugs” — not to do it in some specific manner.
Here’s an interesting quote from one of Rav Moshe’s last teshuvos:
[such food]