In a perfect world, I would definitely want my partners to know each other and get along, maybe even be friends. But in the real world, with our situation, that's less than practical.
My husband works out of town and is only home for a few days every month. My own decision was that I wanted to "dedicate" this time to him as much as possible, since we have so little time to see each other and spend together. So this isn't a "restriction on other relationships" so much as it is a "need of our own relationship" as perceived by myself. i.e. in order for a marriage to work, you have to spend some us-time together every now and then
So he probably won't meet any of my other future-partners until there's something somewhat established and I deem it "worth his time" out of his limited home-time for the three of us to have a coffee.
But my husband and I talk daily on the phone, so he always knows if I'm going on a date or when I start chatting a lot with someone online. If things started getting serious with someone, I would ask my husband if he wanted to talk to that person on the phone. I rather suspect he wouldn't, just because his work schedule is very "work, eat, sleep, repeat" and I can't imagine him chatting it up with a total stranger just because his wife is dating them.