Idiomatic in scripts (and documentation and training). REPL idioms are much more loosey-goosey.
That's actually something I have come to appreciate about Powershell is that idiomatic distinction concept that scripts are more likely to be read by other people (including Future You with no memory of having written the script in the first place) and to write "full sentences" for an audience, but feel free to be fast and loose in the REPL all you want.
Totally agree! I am a bash fanboi with a fish fetish, but recently started in a windows shop. I've actually grown quite fond of the flexibility powershell offers, and how usable it is without requiring esoteric knowledge.
It is idiomatic to capitalize liberally though.