I was reading this article today, by a psychologist on the 'choking' mechanism that can reduce performance, and I think the same argument can be applied to language study - and to Latin in particular. OK,it does not appear to be totally 'hard science', but the general position is evidence based:
Most people I know who try to speak Latin, are afflicted by what one might term 'performance anxiety', when there is so much grammatical analysis going on, that the ability to actually produce any Latin is paralysed. So, they think they can't do it, and give up.
I think that the usual grammar intensive nit-picking method of teaching Latin actually promotes this, and so reduces the language performance level of the students. As language performance isn't a goal, perhaps this is really not considered. Almost no Latin teachers have language performance as a goal. Most seem to have analysis as their goal.
Interestingly, this stress caused by over analysis seems to lower one's working memory.....and so reduced performance
So, just one more consideration, in favour of a more holistic approach to Latin language teaching.