alt Hacker NewsPressure cookers do reduce the cook time of some dishes dramatically, but the flavors don't meld as much compared with slow cooking. If you do a 30-minute recipe like this, it's probably worth letting the soup sit another 20-30 minutes in warming mode before serving.
One of the reasons why I loved The Food Lab was that very often Kenji would write several versions of a recipe at different effort levels, along with detailed reasonings about why and how he shortened a step and what one was giving up by doing so. While he didn't do that for the Pho Ga recipe, he did do that for his Beef Pho recipe, with a full blown 6 hour "traditional" version [0] and a faster (although still not as fast as the pressure cooker pho ga one) 1 hour version of the recipe [1]. My guess is that the write ups of the 3 recipes together probably give one enough information to dial in relatively precisely how much effort you want to give and which steps one can skip or reduce.
[0] https://www.seriouseats.com/traditional-beef-pho-recipe
[1] https://www.seriouseats.com/quick-and-easy-1-hour-pho