This game seems to want to punish people who are QP’ing to help backfill ragequitters or etc.
To prevent this from being abused just make sure the same person reconnecting wasn’t the person that left. Only new connections get full HP/ammo.
If I join mid session and I have 1 HP, low nades/ammo I usually just either RQ or type LOL while the sixteen trillion ragers surrounding me finish the job.