My first fear was that system was messed up because of non calendar year. But I tried an experiment and it worked fine - the employee I entered receivbed 2 years of service for vesting. So, now you force me to use my brain - shame on you.
2 possible guesses, maybe even a third.
1. does ee have 1000 hours this year? or maybe I should word that, is ees current hours < hours in the grid for vesting. This would duplicate results you stated. (2 years participation, but only 1 for service.
2. Is exclude years of service for vesting before plan started? I wouldn't expect this unless you said everybody with 2 years was showing with only 1 year of service for vesting.
3. possibly valuaton date in specs is not set to end of year. I think you could actually run things this way, and it wouldn't be a problem, but when all else fails.
I am more concerned that someone in support said you have to work 12 months the first year to get credit. NO, they are wrong, and I will tell them so. Someone is sadly misimformed.