I've noticed the same thing. Doing all the quests won't get quite all the rewards unless you collect a lot of times ...more than twice a day since that's my average. It may be that since they tend to give them away in the FA that follows they feel we don't really need to win all 9 of them at once?
AJ
The Halloween event was the first one since 2019 where I did not get all 9 artifacts during the event in my US city, and in about a year in my Beta city, and that is without buying any extra currency in either city. In this event on Beta, I finished one grand prize past the 9th artifact and got the owl avatar. In my US city, I will have the 9th artifact tonight, after doing the quest and getting the free 30 from the daily, plus a few more spawns. That will probably leave enough over the final 6 days to get the avatar there as well. And yes, the only time I do not collect at least every 6 hours is when I am sleeping. but I get more than enough 2s and 3s from the spawns, on average, to easily make up for what I lose. Oh, and I never buy the Event building that adds one to all the spawns.
I also have to say that in an event with this system, that 100 extra currency from the newsletter can make a difference for the city you give it to, if you play more than one city on the same account.