Bulk Update for Bid Modifier?

Hi everyone, as the title suggests, I'm trying to see if it's possible to do a bulk update for publisher_bid_modifer. Looking at https://developers.taboola.com/backstage-api/reference/bulk-update-campaigns, publisher_bid_modifier is.... not an option, but when having to do thousands of sites individually as PATCH operations... At some point it may be so long that the cronjob won't be finished before it kicks off again 24 hours later.

I don't know if it's possible, BUT... if it is, I'm POSTing to:

https://backstage.taboola.com/backstage/api/1.0/{$accountId}/campaigns/bulk-update

and my payload looks something like:

{"campaigns":[12345],"update":{"publisher_bid_modifier":{"values":[{"target":"abc123","cpc_modification":1.5}]}}}

Whenever I post it, I get back a 400, the error is usually something like:

{"http_status":400,"message":"Bad request","message_code":"api.action.bad_request.null"}

So... Is this possible, or do I have to patch? What's wrong with my payload that I'm posting, IF this is something we're able to do? Thank you!