WSU employees were originally supposed to declare their vaccination status by August 23 - including whether they had already or were going to apply for a medical or religious exemption (personal exemptions were no longer accepted after that date). They were also supposed to apply for those exemptions by Sept. 10, in order to allow time to review them with time to still get vaccinated ahead of the Oct. 18 deadline (most didn't meet the Sept. 10 date).
Aug 29 is slightly arbitrary. My guess is that Rolo missed the Aug 23 date and Chun told him to get it done.
Everything was toothless until 10/18 - it didn't become a mandate until then. But it was well publicized that this was a hard date. There were dozens of WSU employees who had applied late and their exemptions hadn't been reviewed by the 18th. They stayed home on the 19th.
Besides...mandate or not, if your boss told you to get something wrapped up by a certain date, and you didn't even start the process until a month later, that seems pretty insubordinate.