Zard is often an enigma to me. Though, milestone purpose isnt all about keeping characters the same level. It is also about removing a focus (which my players were entirely obnoxious about) on XP earning activities instead of engaging the narrative organically or in a way that interested the players.
A few examples;
GM: (every time I mention there is a door anywhere)
Players: OHHHHHHHHH IS IT LOCKED AND CAN WE PICK IT FOR XP!?
GM: "Bats fly out of a cave as you peer inside of it." (simple flavor and atmosphere setting notion)
Players: OHHHHHHH CAN WE SHOOT BOWS AT THE BATS AND CAST MAGIC MISSILE ON THEM FOR XP!?
GM: There is a fork in the road. A path that winds to the left with footprints of a beast you have been chasing, and a path that winds to the right.
Players: THE RIGHT PATH IS JUST EXTRA XP BUT WE PROBABLY NEED IT TO LEVEL FOR THE BEAST WE ARE CHASING. (actual discussion at table)
I could go on and on but I dislike the things above. It felt more like the players wanted to sniff out XP then to actually engage the narrative and setting. Everything was like a carnival shooting gallery and the GM expected to be a screaming carny with cheap prizes everytime they tossed a dart into a balloon.