The last thing I'd want as a developer or manager is to wake up in the morning with a PR shitstorm and enraged users because I shipped some vuln.
What full disclosure does it put everyone on the same footing. Developers, users, and attackers all at once. It reduces the window for potential abuse as much as possible. As policy, it sharpens the incentives to be very careful in your development processes and improve security measures.
It's worth considering that this is actually a long-running historical debate. One of the commonly espoused positions is yours - contact devs privately, give them a reasonable amount of time to patch, then disclose after a patch. After all, it minimizes disruption to production planning and workflows and still protects users. Seems reasonable right? Everyone wins!
Catch is, it's historically been abused by companies more interested in their production schedules than the security of their users. Maybe that's not you! In which case, well done, you're completely awesome! However, this has historically turned out to be rather a lot of software companies.
Full disclosure, the policy I advocated for, seeks to short-circuit this. It offers maximum information to a maximum of people in a minimum of time. It pressures companies to fix their products rapidly and to ship better products in the first place. It also offers users the ability to be aware that they may be under attack and protect themselves in lieu of a patch which may or may not ever come into being.
At the end of the day, the question is this: who are you protecting with your disclosure policy? I would suggest that the policy you have advanced seeks to balance the interests of users and of developers/managers. It's perhaps worth considering that your users may prefer a policy that aligns your incentives more with theirs. Perhaps your customers might prefer policies that encourage a proactive stance.