Fitness+ is not off limits without an Apple Watch, the issue is that without a watch, users can’t install the Fitness app from the App Store (it errors with the “missing features” message). You would have been able to sample Fitness+ on your iPhone if you hadn’t deleted the app, as Fitness+ can run on iPhone/iPad (not on Apple TV) without a watch being present.
Oh well, you can still sample Fitness+ using your husband’s setup. My wife has a watch but it’s old and not compatible, so she’s going to wear my watch to try out Fitness+.