Shy
Your 'N' had a faulty trim release system then. This would have been due to trim release power defect, trim release switch / wiring defect etc.
Blade
Yes, you were and are spot on. The only exeptionto the rule is if you carry out a rapid turn, climb or decent eg: 60 deg bank angle. Again (As expected) the trim system will not cope and here you may have to momentarily press the trim release switch on the cyclic to effectively resychronise the system.
However, normal flying (Rate 1 turns etc) you should be able to engage higher modes (HDG, ALT HOLD etc) and fly complete hands off without any problem at all.