I personally wouldn't judge a person for taking in a stray with the intent of rehoming them, but enjoying one another's company in the meantime so long as the usual caveats (i.e. all willing, no harm, no coercion, etc). I perfer it when people are emotionally involved with their partners, but I don't feel that's mandatory to be ethical; one just needs to treat them well and respect them.
Some questions I would ask of someone who said this is what they were doing might be, "How long do you keep a dog?", "What happens when you can't find a home?", "What are you doing to help the dog integrate into a new home?", "What criteria do you use to evaluate the home you're putting a dog into?"
It's not enough to just pick them up and house them if we're not trying to get them into good homes with people who will care for a dog as we might; a poor home where they would be mistreated could be worse than doing nothing at all.
Edit: I've taken in dogs before; when I do they become my responsibility, not just to care for, but to ensure that level of care continues when they leave. I'm an active agent as I expect updates, I expect to hear about problems and am happy to provide behavioral support where needed.