I’ve noticed this with a few words, most recently with 大切. If you listen to the little voices that pronounce it (I do to help my memory), Kyoko says “taisetsu”, and Kenichi says it like “taisets”. The greater internet tells me that the final U should be silent (like how Kenichi pronounces it), but do women pronounce the U? Is this considered a feminine way of saying it? Is that why Kyoko does it?
I’m not at the point where I’m able to actually listen to Japanese speech so I have no idea.
I’m not aware of anything to suggest that the つ in 大切 “should” be devoiced.
As far as I can tell, the vast majority of differences between specific things Kyoko and Kenichi do that I’ve heard people point out over the years are attributable to individual differences, not gender or anything else.
I’d recommend using sites like forvo or youglish if you want to hear more examples of natives saying words when you’re unsure from listening to the examples here.
EDIT: for what it’s worth, the lone male recording for 大切 on forvo voices the つ
Whenever I ask these kinds questions of my Japanese friend, she will almost act like there is no difference. Same with des or desu. She seems to not care if you do or don’t voice the u. She gets on my case way more about not pronouncing “n” for long enough. Or horrible pitch accent.
Personally I wouldn’t use up my brain space on this particular quirk of pronunciation.
I feel like Japanese pronounce things differently in isolation. You’re recommendation of youglish where you get a whole sentence is probably more useful. Japanese in isolation will often revert to what they feel is “proper” Japanese.
If you ask an English speaker “how do you pronounce ‘comfortable’?” you could get an unnaturally slow and exaggerated “COM-fort-able”, but then the same person will say “comfterble” in speech.
In one of the films from the JFF this year - My Broken Mariko - one of the characters voices an U from ます in one of their sentences, then devoices it from です a couple of sentences later (or maybe it was the other way around, first devoiced then voiced), all within the same dialogue - and it wasn’t because of surrounding words, just obviously personal preference, perhaps to add a bit of emphasis or just getting carried away by the dialogue’s contents.
I’ve watched quite a lot of Japanese films this year (I’m at 80 at the moment) and, while most of the characters devoice the U in ます、です、つ、少し and so on, a significant number do not. Gender did not seem to play a role, although maaaybe a few more ladies voiced it compared to men on the whole.
Personally, I prefer the voicing whenever either is possible… it sounds nicer to my ears