I just said to my dad (with whom ds and I live, rent free, does that make me not a single mom?) that the only thing more emotionally draining than going to work all day and coming home to be a parent would be going to work all day and coming home to be a wife.
I was thinking specifically of my own ex, I'm sure there are lots of guys who are a pleasure to come home to. I also don't go to work all day, for the record, dad and I were talking about commuters at the time.
As we've said before, "single parent" is so broadly defined, and marriages vary so widely I don't think "I'm like a single parent" really means much out of the context of who's saying it. The person who says it probably has something else they're trying to express but doesn't have the words, or doesn't feel comfortable saying, "I feel lonely," "I miss my dh," "Taking care of a house and family 24/7 with no breaks is exhausting," etc. It's sloppy use of language and inconsiderate, but I think it's forgivable.