I follow artists who take about 5 slots at a time and have deadlines of 2-3 months and non of them use Trello. Yes, some artists work with queues or it's just easier to keep a schedule like Trello but I think it's a pretty dismissive comment to many artists who don't use it.
If you're getting a commission from an artist, ask if they have a public trello, if they don't have that or an alternative DON'T COMMISSION THEM.