If you read the comment section on the original site they're saying that their devs use Chrome so Asana ends being more optimized for it.
"I went to interview for a front end position at a big company and in the interview, I wrote a very optimum JS code for something and I got laughed at, the interviewer saying in this era of 64GB rams and stuff why do you need to bother about optimising JS"
sorry, can't find the source.
And of course your software is the only thing they have to use that computer for, so it's perfectly fine to consume every last scrap of resources it has.
I miss the 2004-era web, where the most resource-consuming webpage was the one where some idiot posted a dozen thumbnail-size images but forgot to actually thumbnail his camera's enormous 2MP images.
I'm using Chrome too.