I noticed something very interesting in the adaptations of the novel 『バッテリー』 across media forms. For context, the story is set in a fictional city in 岡山県. The protagonist 原田巧 is described to have been born in Tokyo and moving around with his itinerant family due to his dad's job changes. At the beginning of the story, the family move to 岡山県, 巧's mom's 実家.
In all the media adaptations, the people in that small 岡山 city speak with a very distinct accent. But interestingly, in its movie adaptation which came out in 2007, most local male characters, from barely teenaged elementary, middle school kids to middle-aged teachers use the first person pronoun わし. This is the only place where I've heard teenagers refer to themselves as わし. But interestingly when the TV drama came out in the following year, the markedly western accent is kept while the male first person わし is all changed to おれ. The anime came out much later in 2016, and it followed suit in discarding わし as a dialect marker: just like in the TV drama, you hear the accent but not the unique use of the male first person pronoun.
Sadly I don't have access to the book (This 試し読み that I found cuts off right before the first scene with local kids) or the radio drama which seemingly came out in 2000, so I don't know which personal pronoun is used in them.
I have read every answer under this question, and they appear to address わし's use by older men, which I guess is more of a general 役割語 and has enjoyed wider and more lasting currency. I am also aware that in 愛知県（三河弁） some females use this pronoun, but that's outside the scope of this question.
Wikipedia 日本語の一人称代名詞 contains similar information.
My question is
Is the change of the local male 一人称 in media adaptations in any way indicative of actual usage change over time? Namely, did young male users of わし in those areas actually dwindle in the past two decades?