iPhone SE 2020 audio routing issue with Bluetooth microphone

I've noticed recently that when connected to a bluetooth headset, my speech in some applications still seems to be recorded using my phone’s microphone. I would expect my bluetooth device’s microphone to be the source.

Apps that use the Bluetooth microphone: WhatsApp, Voice Memos

Apps that do not use the Bluetooth microphone: Snapchat, X, Blood Strike

Steps to reproduce:

1. Connect bluetooth earbuds to your phone

2. Record a voice message in chat of the listed apps, with your phone far away from you.

3. Play back the message

Actual result: Some applications do not use the bluetooth microphone.

Expected result: All applications should use the bluetooth microphone.

My built-in microphone is busted, so this is very frustrating for me.

Device: iPhone SE 2020

iOS verison: 18.2

[Re-Titled by Moderator]