i think it takes the last choosen profile, for me it does so. {And Gnome is doing it mostly like this}… your device must be able to get connected with a2dp !
You can take a look:

pacmd list-sources

will give you something like this:

index: 3 name: <bluez_sink.00_12_3D_00_3D_1C.a2dp_sink.monitor> driver: <module-bluez5-device.c> flags: DECIBEL_VOLUME LATENCY state: SUSPENDED suspend cause: IDLE priority: 1030 volume: front-left: 65536 / 100% / 0,00 dB, front-right: 65536 / 100% / 0,00 dB balance 0,00 base volume: 65536 / 100% / 0,00 dB volume steps: 65537 muted: no current latency: 0,00 ms max rewind: 0 KiB sample spec: s16le 2ch 44100Hz channel map: front-left,front-right Stereo used by: 0 linked by: 0 fixed latency: 45,32 ms monitor_of: 2 card: 2 <bluez_card.00_12_3D_00_3D_1C> module: 28 properties: device.description = "Monitor of BH-M30" device.class = "monitor" device.string = "00:12:3D:00:3D:1C" device.api = "bluez" device.bus = "bluetooth" device.form_factor = "headset" bluez.path = "/org/bluez/hci0/dev_00_12_3D_00_3D_1C" bluez.class = "0x240404" bluez.alias = "BH-M30" device.icon_name = "audio-headset-bluetooth" device.intended_roles = "phone"

You can see a2dp_sink.monitor for the headphone…
[card: 2 <bluez_card.00_12_3D_00_3D_1C>]
With:

pacmd set-card-profile 2 a2dp_sink

where 2 is my headphone yours can differ…

you can force to enable a2dp after connect the device also… i do not know how to automate if Gnome-Bluetoothn does not recognize your last settings

Cannot pair bluetooth Headphones