Why do the Cork-Dublin train have lower spec carriages than Heuston-Newbridge trains?

[2200DMU]

22000 (first class when possible) will be operating the 15.00 to Cork and 18.30 return service on Mon-Thur for a number of weeks. This is to allow the Mar4 sets a deep cleaning progame. I also think the 15.00 today was a 22000.