there are many forum threads discussing this topic and providing explanations for why users add confirming IDs to already RG observations. Have a read of the following examples and hopefully they will be useful for you:
https://forum.inaturalist.org/t/why-do-some-observation-receive-plenty-of-agreeing-ids/37287
https://forum.inaturalist.org/t/in-defense-of-the-thousand-confirming-identifications/53528
you can turn off notifications for IDs that exactly agree with yours; this is done in your profile settings