| The app is correct, both of those phrases are passive. Grammatically the passive voice uses the equative verb to be with a past participle of the verb. Both those phrases satisfy that condition. Semantically, the passive voice involves action being done to the subject. Both those phrases also meet that condition. Rearrange them and you'l see: [1] "I was exhuasted" --> "${SUBJECT} exhausted me".
The phrase may not seem passive because you've elided the subject, which is part of the problem of the passive voice, it lacks clarity [2] "Our work here is done" --> "We completed our work"
Like the first phrase, this phrase elides the subject of this sentence, the individuals doing the work. In this case, including the subject ("We") may feel repetitive because of the pronoun "our", but its still more precise. Also, passive voice isn't bad, however it most often lacks clarity. Sometimes that's okay, and sometimes you want some flexibility with your sentences for effect, such as ending a sentence with the subject (one of the primary reasons to use the passive voice). |
I don't think that a correct analysis of the sentence. The exhausted is an adjective, similar to I am tired, but saying "Something tired me" would have a totally different meaning, because it's a different, unrelated sentence. ("I am covered in green paint." also doesn't seem like it's passive voice, but maybe I'm wrong.) As far as I can tell, "our work here is done" is indeed passive voice, but it is also perfectly fine English, and thus must not be highlighted.
"I was exhausted" absolutely does not "lack clarity". What could it possibly be unclear about?
Looking at http://www.lel.ed.ac.uk/~gpullum/passive_loathing.pdf, I'm also suspicious of your definition of passive (p.7):
> ...passives do not always contain be and do not always contain a past participle. They also do not always obscure the role or responsibility of the doer. They may or may not have a subject (the passive clause in any monument defaced by vandals does not), and they may or may not have a by-phrase (The president has been assassinated does not). Sometimes they specify the agent of an action very clearly (as in It was thrown at them by hooligans), and sometimes not (as in It was thrown at them); sometimes they specify the undergoer (as in A surfer was attacked by a shark) and sometimes not (as in Being attacked by a shark is no fun). Often (as in (3)) there is no action whatsoever, rendering the strange phrase “receives the action” inappropriate.