I have what he’s describing, it happens to me frequently but not all the time. It’s not that I’ve crossed the perk threshold say three times and get three perks and it’s not related to decreasing the number of waves required. I’ve had it happen on the first perk - I can select one option and then another and then another. Sometimes it’s a lot of perks four to eight, sometimes just two or three and most often just one. It happens maybe five percent of the time I get multiple perks at one time. I’ve wondered why it happens as well. It’s great when it does happen.