It sounds like Wallace is very good at reading exactly what Finley needs. That’s great! There ARE bigger dogs like that. You just have to be SO careful about it, because many are not!Finley loves to wrestle with our 45 pound Aussie mix, Wallace. Most of the time, Finn will initiate play, and often, but not always, she's on her back. We are sometimes reminded of a cheetah eating a gazelle on the Serengeti! (But he doesn't pin her down; she's always able to get up.) She also loves for him to chase her; if he stops, she'll run up to him and get his attention. Occasionally there's a very small yip, but he'll stop play immediately and walk away, and she will come after him again, as if she's saying, "no, we're good, I'm fine. Let's play!"
But I agree that play with a bigger dog needs to be monitored and you need to watch for signals from both dogs.
When Tessie, our lab, and Wallace play, they are rougher with each other. Finley does not get in the mix for that, but barks from the sidelines, as if she's the referee.