Just wanted to connect to confirm here, having taken a closer look. The bulkOperations doc shared outlines functionality in the Admin API, however the reference document shared is for ProductVariant object - of the Storefront API.
Looking closer at this ProductVariant object doc for the Admin API - you can see that there are no “priceV2” or “compareAtPriceV2” fields. My suggestion would be using this reference as starting point to retry, I had no issues in testing with this on my end.
In terms of the product variants webhook, this returns data from the Admin API. The data returned via the Storefront APIs and the Admin APIs can differ and each provide different avenues of functionality to build with. Just to confirm, the fields and objects mentioned are currently working as intended for both the APIs and webhooks mentioned.
While I couldn’t find a direct solution or workaround for your use-case, I would be happy to pass on some feedback on your behalf. Please understand we can’t make any guarantees that feedback is actioned.
I would also encourage you to keep eyes out on these community forums for related topics. Hope you find a solution - Cheers!