Listing an unmarried woman as "daughter of ...." and the father's occupation is quite normal, and a widow in terms of "widow of ..... " and his occupation, so I certainly wouldn't call it unusual.
The questions asked (and the information recorded ) on any registration derive from the various Acts of Parliament, and specifically the GRO instructions and manuals in force at the time. However when you look at certificates it is clear that from the beginning, and still today, registrar's have always interpreted those instructions with some degree of latitude.
I have seen many examples of the wording you describe, but also some that clearly don't follow that pattern, so it is impossible to draw a definitive conclusion from the wording alone - it needs to be checked against other known sources (as you are doing).
Did they collude to give false information ? People certainly did, and still do, lie to registrars, but the question should always be "why would they ?" "What would they gain by doing so" ?
Whether the informant knew the correct information to give is another matter..... what was the qualification of the informant that allowed him to register the death ? How likely was he to know the correct information ?
In my experience, even today it isn't unusual for those registering deaths to get things wrong, or just not know ..... even things like their own mother's maiden name.