That is a very interesting conversation bigsciota.
I learned to play on a small embouchure renaissance style flute, and though music (more classical) is definitely not whistle like on it, when playing faster traditional music at speed it definitely wants to come out more “notes than expression”. I don’t mind that at all personally, especially if it is fluid or graceful as well, some of Paddy Carty’s playing comes to mind in that respect ?
Any tune just for the sake of it is not going to lift me though, and that seems to count especially for “whistling on the flute”… because I am much happier listening to the the actual sound the player is expressing if the rest is “just repetition”, if that sound has some natural feeling to the voice. Most flutes are capable of this expression if the player chooses to accept it, even the renaissance flute. Some are much better though… the Rudall Rose flute seems to be very vocal, which Catherine McEvoy plays for example. I know it can be played more directly, but its voice is there if accepted. So if you listen to her or say Josie McDermott properly , you will hear the flute literally lilting along the song (I know the word tune is supposed to be used) . Chris Norman also I think.
Player embouchure is very important, I think pursed lipped playing favours rhythm over expression. Matt Molloy is capable of all the styles I should imagine, I find his playing clean with a lot of expression but definitely not whistling. The tongue does not much help the shaping of a deep tone , and use of interrupts the melody. His playing is beyond further comment (or praise even) by me, because it is very complete. When I listen to his playing it is like he is saying “don’t listen to me, listen to the music” 
For gentler tunes the renaissance style flute actually can be played close to his way of playing.
Funnily, I did try to copy the first of
https://m.youtube.com/watch?v=5FSK4bmYspw
onto flute just as she plays it on whistle. In the end after a lot of effort, I decided it is not possible to get that brightness and liveliness on flute. So you can’t whistle on the flute even, only sort of try to 
Really important I think is setting. If you are playing in a band for example the flute is played a certain way. If it is lead or solo, another way. If it is noisy street corner another way. If it is alone or in quiet company, yet another way is possible.
Own surrounding will also influence. Students will tend to emulate “the whole show”, so at home when quiet they might still be practicing to play on stage a certain way. So it isn’t just the music, but all that might go along with it.. friends, making impression or fitting in…even just what a player feels represents their own character at any point in time. That is fine also. I have played mostly guitar for example, learned many styles and reached the level where apart from now being able to play own accompaniment in whatever way I find natural, when looking for what next was looking at say Mark Knopler and a few others that really make the instrument sing… and am capable of that… but next beyond that and not just copying ? Which is a reason I learned to play the flute, because it has the expression and sustain (without amplification) and closeness. It was that or violin, but violin is not my character…though I am learning a tune as played by Tommy Peoples on violin and that is very rewarding
.
Anyway, when out walking in forest a lot it says “A Flute” .
So I guess “each to their own” really, you cannot force appreciation of certain subtleties on others, and where they are being lost is more a reflection of how the world is nowadays than any ignorance by musicians. I just repeat that learners should be encouraged and supported in exploring the full capabilities of their flute and styles/methods of playing. They should do this by themselves anyway but it isn’t that obvious when starting, especially when with a set objective of how anyone thinks they want to play.
Maybe I sound like I know a lot, or am accomplished, but not so, it is just that this is all still fresh to me from having done much learning and in a relatively short space of time. Now after a year and a half I know quite well what playing the flute is about…but only know about twenty tunes and only play less than half of those as I feel to. There is no rush and have more than enough to suit any mood… the difficulty is that I keep hearing new tunes I think I have to definitely learn while also knowing that to learn a tune properly takes “quite a while”.