Agree with you that it makes sense to carefully understand what is covered by the policy including reading policy or contacting the company if necessary.

With that said, my experience actually was the opposite. Most policies I've seen would include bicycle touring and then have a rider for additional sports activities. Two examples:
- World Nomads has bicycle touring in standard list and other stuff on expedition: https://helpdesk.worldnomads.com/cus...ticles/2402086
- IMG Global has an adventure sports rider for mountain biking and other stuff though bike touring not on that additional ist: https://www.imglobal.com/travel-medi...rance/benefits

Often there are some things on the "sports rider" packages that I might do anyways in addition to bicycle touring - so will often compare the policies and as necessary buy the rider.