June may be too late in the year, but some credits have an income cap.

I'm not the poster who mentioned this, but I assume they're thinking about tax brackets. If you make a year's worth of income in a year, then take a year off starting in January, some of that income may be taxed in a higher bracket. If you take a year off starting in June, then you make 1/2 year income in one year and 1/2 year income in the next year, so there's a better chance that all the income will be taxed in lower brackets.