There has been a long trend involving the use of opst period sources for earlier forms of cooking and they can make very valuable additions to anyone's library, however, it is wise to know why we are using them and to understand both the oop (out of period) recipes as well as the older.
Back when I first started to study medieval cookery, there really wasn't a lot available for most amateur historians, even 19th century stuff was not so easy to come by unless you owned original sources (which is what got me interested in historic cookery in the first place). This is why I suspect the Edward Kidder book and Martha Washington book became so popular in the SCA. Though arguable that some recipes were quite old, the underlying reason was because period sources were rare and hard to find. There were a handful of books popping up, mostly 13th-15th century stuff and difficult to read for many and even with more, not a whole lot of the familiar foods people were craving or wishing to start out with (either because of being unfamiliar or lost without better instruction) and thus the popularity of more great 17th century books, such as by May or Markham. I will kid you not, these are great books, but then I am partial to English 17th century cooking.
The problem I am finding today is that the English 17th century library has been accepted and brought into the fold of pre-1600 era cooking, and this is wrong. At least it is partially wrong. The problem is basically where new cooks will refer to these generally accepted books without knowing why they are acceptable and may unwittingly assume a dish made in 1630 would have been known in 1590. This may or may not be true, we simply can not make that assumption, we can't even assume theories speculating that food fashion has a 20-30 year time frame of error once it hits print. A whole knowledge base of food existing in one book can't even be generalized as having the same time-frame of birth in popularity or popularity of that time. Both fairly brand-spanking newer recipes and hundred year old recipes have been recorded in the same books, indeed it takes a much larger library and much reading to get an idea of when certain foods seem to rise and drop in popularity. Even foods that share names go through a sort of evolution and in as little as a decade. The real issue, as with clothing fashion, architecture, writing and many other things, nobody really seems to be deciding that hey, it's now 1500, time to do it all up new again. It's messy and random. A new trend from 1562 can very well cease to be all the fab by 1578, though it doesn't mean some trendy diners won't hold on to some favourites. As well, we can see new foods pop up in 1589 and more again in 1603 and 1618 and so on and these guys are trendy writers. Sure, some things are going to be those favourites that just won't die but it doesn't make the whole body of work printed oop plausible for food within period. It is up to us not to treat a body of work as one, but to look at each and every recipe on it's own merit.