The problem is not new, though. The article opens by mentioning a 1926 concert in which the choir asked the audience "If you sing tenor, please join us." The tenor range is relatively rare among men's voices. I'm a high tenor myself; I can routinely sing a G, and I can get up to an A if my voice is in good form. I think I managed a B♭ (Bb if HN strips out the ♭ (flat) Unicode character) once, but it was decades ago so I'm not sure if I'm remembering the arrangement correctly; and choral arrangers rarely ask tenors to sing a B flat since they know so few people can handle it. Pretty sure I've never been able to hit a C, though. (C5, that is; of course I can hit a middle C).
But tenors have been in short supply for decades and decades. Every single time I've tried out for a choir, when the choral director hears how high I can sing, I can see some sort of "tell" on his or her face. A smile, a widening of the eyes... I can sightread, too, so I know I'm a shoo-in for any choir (well, any amateur choir at least: I'm not a music professional and wouldn't be able to devote 20+ hours a week to a choir). But I suspect that even if I couldn't sightread at all and had to have my hand held for any new piece, choir directors would grab me anyway, just because of how high my voice can reach if I haven't been abusing it.
The general guidance if you are writing for amateurs is to stop the tenor and soprano sections at their respective "high G" and if you are writing for professionals to avoid going above their B. Amateur choirs will often sing music written for professionals (eg all the masterworks), and you will end up getting A's or Bb's but without expectations that it will sound good.
But tenors have been in short supply for decades and decades. Every single time I've tried out for a choir, when the choral director hears how high I can sing, I can see some sort of "tell" on his or her face. A smile, a widening of the eyes... I can sightread, too, so I know I'm a shoo-in for any choir (well, any amateur choir at least: I'm not a music professional and wouldn't be able to devote 20+ hours a week to a choir). But I suspect that even if I couldn't sightread at all and had to have my hand held for any new piece, choir directors would grab me anyway, just because of how high my voice can reach if I haven't been abusing it.