minecraft.used:minecraft.map don't increment score unless in a stack.

Recreation:

• Create a scoreboard objective using this command:

/scoreboard objectives add usemap minecraft.used:minecraft.map

• Use this command to display the score in the sidebar:

/scoreboard objectives setdisplay sidebar usemap

• Give the player a single map and another stack of 2 or more.
• Use the singular map.
• Then use one map of the other stack.
• The score doesn't change the first time, but it changes the second time

Notes:

Tested in survival and creative.

Tested in versions: 1.12.2, 1.13, 18w30b.