Well yes, but this has been my confusion. In some places it seems that the two year exemption includes any time you have spent in the US in a calender year.
See 'Example 4' here on the IRS website:
https://www.irs.gov/individuals/international-taxpayers/tax-residency-status-examples
I've also come across a similar example explained on a different thread:
https://ttlc.intuit.com/community/college-education/discussion/j1-research-scholar-2-5-years-in-usa-...
Very frustrating if that is the case! - a date based system seems much more reasonable.
