Why all metafield changes trigger 'PRODUCTS_UPDATE' metafield ?

[seymur_crsp]

Hello. I have created a "PRODUCTS_UPDATE" webhook subscription and specified that I want to receive updates to metafields under "bundle" namespace. But seems like changes to any metafield triggers the webhook. For example if I change a metafield that is under "custom" namespace, it also triggers the webhook.

Why is it like that ? How can I prevent it ?