The Bug:

minecraft.used:minecraft.candle doesn't increase when placing a candle on to a cake.

Steps to Reproduce:

• Create a scoreboard for minecraft.used:minecraft.candle

/scoreboard objectives add use_candle minecraft.used:minecraft.candle
/scoreboard objectives setdisplay sidebar use_candle

• Place a candle.
  →  Notice how the scoreboard increases.
• Place a candle on top of a cake.
  →  Notice how the scoreboard does not increase.