For Igloo home, your point2 still valid? if the lock spoilt, will be trapped inside home?
"Still valid" ? Yes, until there is information to the contrary.
Longer reply:
However, the judgment is best made relative to the alternatives. All digital locks may fail. Some may have higher probability of failing: the design, the materials, the QC, and don't forget the USER (being the biggest variable that we forget about). Even regular key locks fail (which is why you have locksmith stickers pasted on every HDB door frame). So the judgement to be made is a relative one. There is no binary answer to whether you need to have the knob or not. However, if you miss out the pleasure of digital locks knowing there is a missing knob, and that gives you sleepless nights, then it is more important to have one.
Digging a little deeper may provide a little more context to how you judge the importance of the manual knob.
The unlocking of the bolt and latch (from inside) for this type of lock is mechanically driven by your hand pressure as you pull the handle. This handle is your effective "manual" unlock (no electronics involved) from a layman's perspective: it engages the mortise (the component that eventually locks and unlocks the door) through mechanisms (gears etc ) inside the lock. The probability of failure (of. The handle) would be higher than say the manual thumb turn by virtue of mechanism complexity and components involved. The thumb turn is a much simpler stick that goes right into the mortise core. All said, no one knows statically the failure rate other than the vendor or the manufacturer, and over time.
Perhaps an alternative way to look at it: the vast majority of turn handle digital locks have manual thumbturns where the inside handle already serves as the default manual opening. Why did these manufacturer incorporate the thumbturn knob at additional cost (and opportunity cost of rerouting around the shaft that the knob turns) when both are manual opening mechanisms?
Why didn't Igloohome design it into their lock? The simple answer could be that they are not a lock hardware manufacture: it was sourced from an ODM and that ODM has yet to embark on fully automatic mortise generation of locks.
If one has a choice/flexibility, buying a lock made by a top tier original lock manufacturer is a good approach. Re-labelled, white-labelled brands are sometimes constrained by choices at contractual time.
PS. Notice that fully automatic mortise models like
Lockin S30 Pro or equivalents have the thumbturns. I believe this newer generation of locks frees up the internal space that was previously occupied by the manual push pull handle mechanisms.