The severity of financial impact on the victim is irrelevant. If I steal tiny amounts of money ~0.01c from large amounts of people and accrued significant wealth from it, is it fine? Is it a "victimless crime" because the amount is so small?
Not if it actually damage some parts of the phone like the battery because you have to charge it more often.
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Do either of these apps explicitly state that they will access/use device in this way?
Someone cuts down trees from land they don't own to haul them away for lumber? That's clear theft to me.
Removing furniture that you don't own from a cohabited dwelling and storing it without telling the owner the location? That's clear theft to me.
Someone finds lost goods that they then keep for themselves without attempting to return them to the rightful owner? I can see that being something other than theft.
Taking someone else's property can be both theft and conversion.
Conversion is a tort, a matter of a lawsuit between parties.
Theft is a crime, a matter between a citizen and the state.
Edit: Just a note, I'm not saying this is OK for apps to do, but to call it a theft is ridiculous.
I can think of at least two differences. First, the developer profits from one but not the other. Second, the developer intended one but not the other.
We evaluate the morality of accidental waste differently from that of deliberate taking for personal gain.
On the other hand, if you look at this from another perspective, inefficient software wasting power means no one gains. If the same power was being used for mining, then someone gains. If I were forced to choose between these two alternatives, I would definitely pick the latter.
And, all else being equal, if someone writes inefficient code and has bad intentions, it's even worse.
Is one of those considered stealing?