There are often debates about the “correct” traditional forms of certain characters.
I just came across the following sentence:
我們不能以今律古，將今天纔有的種種概念，如共同語、地域分支、標準語等等，强加於古代的語言現象。
Now, being a book talking about language evaluation, I’m sure that the authors chose 纔 to represent 才 because it is somehow the more accurate form of this character. I don’t really know the rational behind this reasoning though.
Why is 纔 the “correct” traditional form of 才?
I'm assuming that you're not talking about the trivial kind of "correctness" where one country/region defines some standard of character usage, and anything outside of that standard is "incorrect".
It's not.
There is no "correct" form of a character representing a meaning like only; just; merely, because there is no character which was created for this purpose. This is unlike some other character pairs, where you can be sure that one variant is more "correct" than the other, or at least has a much better historical precedence (e.g.「气」is definitely "more correct" than「氣」; the former depicts the word it originally represented, while the latter is a phonetic loan).
Bear in mind what the book you're reading is actually about; apart from the possibility that the choice of「纔」over「才」is just as a result of personal preference, there are real disambiguation reasons for which one might choose「纔」over「才」:
If one is talking about language, especially archaic texts, the chance of reading ambiguities popping up is much higher with「才」than「纔」.
I'm assuming that you're not talking about the trivial kind of "correctness" where one country/region defines some standard of character usage... is to get people to look beyond what each country or region is doing with their character standards, and to actually think about the characters themselves. In many cases, there are choices with better historical precedents, regardless of what the governments are doing.
Due to the complicated strokes, the traditional form 纔 is being wholly replaced by the simplified form 才 even in Hong Kong and Taiwan.
I was from Hong Kong, no one would use 纔 instead of 才. Just look at how many more stocks in 纔 compare to 才. I would consider 纔 is the archaic form of 才
Why is 纔 the “correct” traditional form of 才
It was the “correct” traditional form of 才 but now is archaic (almost no one use it nowadays). 才 is officially the standard (in traditional or simplified Chinese) in modern Chinese. 纔 had became a rarely used variant (it is not incorrect but it is very old fashion)
BTW, the argument in the text you posted is about "We shouldn't insert modern concepts in ancient language". If it was written as 纔 in the first place, just leave it that way
