Setting partitions in platformio.ini instead of skdconfig.defaults? espidf v4.0

if I set the build flag in my platformio.ini
board_build.partitions = partition_custom.csv

Does it get built into the sdkconfig during the build process?
I am getting this as a result, which is the default setup if nothing is set.

CONFIG_PARTITION_TABLE_SINGLE_APP=y
# CONFIG_PARTITION_TABLE_TWO_OTA is not set
# CONFIG_PARTITION_TABLE_CUSTOM is not set
CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions.csv"
CONFIG_PARTITION_TABLE_FILENAME="partitions_singleapp.csv"
CONFIG_PARTITION_TABLE_OFFSET=0x8000