Google target-based bidding behavior changes on August 17.
Google says budget-limited campaigns using Target CPA, Target ROAS, or Demand Gen Target CPC will follow their stated targets more closely after August 17.
Check Review targets before August 17.
Why it matters and sources 1
Who should care
Search, Shopping, Performance Max, Demand Gen, and eligible Travel advertisers with campaigns that have been limited by budget.
What to check
Compare every stated target with recent actual CPA or ROAS before August 17. Export the current settings and results, then wait one to two conversion cycles before judging the post-change account.