It's worth considering if those Polymarket resolutions for June 19th and 20th truly needed the later military strikes to resolve as 'No outcome'; perhaps the simpler explanation is that no action occurred on those specific days.
It may be that each market operates more like a separate daily lottery draw, where the outcome is decided by what happens within its own timeframe.
For instance, if you bet on whether it would rain last Tuesday, and it didn't, the result is 'No' regardless of a storm hitting next Monday; the timeframe for the bet had simply passed without the event.
Each market would have its own closing conditions and dates, and once those pass, the outcome is recorded based on what did or didn't happen by then.