Confused on suggested ES tax payment schedule

My friend made a significant sale a few months ago , and I'm a bit confused on why the accountant suggested he should wait to send an ES tax payment until september.

When he filed his 2025 taxes he was told because he overpaid instead of getting a refund the anount would be credited towards his 2026 taxes and the estimates would likely cover the year so he wouldn't need to make any estimated tax payments. So when the sale went through because it was higher than previous year sales I asked if he should send an ES payment just to be safe, and if so how much.. but the accountant said to wait until september then send $1,300..

Just wondering…. Why is that? Does it really matter when an ES payment is sent?

I thought the primary goal was to make sure you send the proper amount due for the year within the year , particularly if your self employed and the waves of income don't line up with the tax quarters.