fabbe92, whilst I was at OAA, BA (the only UK airline to take integrated students only at cadet entry level) said the reason for this was that they had experienced "significant training failures" from pilots on the Self Improver route (the fore runner of Modular) at cadet entry level. Their decision had nothing to do with status. So they say.
Maybe smaller airlines can experience similar problems and make similar decisions? In Jet2's case it would be surprising as (if you check Oxford's website) they haven't taken anyone from Oxford for a few years.