I agree that this is a bit of a limitation. I eventually copied the Walk activity and renamed it "Hiking". I now use that new activity and it all comes in ok. You still need to select "Walking" from the Activities menu, but as long as you remember that, all good.
I have just received a new Forerunner 945 for Christmas, and I have been struggling with the same issue. It appears the Garmin Direct App still hasn’t been updated to include the Hiking activity (and others). You simply don’t appear to be able to add it as an activity. I am not sure why it is even offered as an option if you can’t see basic 7d, 4w, 1y stats. I contacted Garmin a few days ago but as yet I have received a response. Unfortunately I also don’t have a clue how to change my recent activities (since Christmas) over to walking or running. Everything worked just fine on my FR 620 so this is s real disappointment. Come on Garmin get your act together, it’s been over 4 years since this problem was first highlighted!
If you want to change the type of an activity then view the activity, click edit (app or web) and change the activity type.
If you want a report you can use Progress Summary and select Hiking as activity: https://connect.garmin.com/modern/progress-summary
You can also use the other reports: https://connect.garmin.com/modern/report/16/all/last_seven_days
Just remove the activity types you are not interested in.
Thanks so much for your response, I did eventually figure out how to change over my recent activities to ‘running’ this afternoon on the app. I can now view all my 7d, 4w, 1y distance stats again. I don’t personally care about specific activities these days (whether it’s running, walking or hiking). I know others do and that’s fine. It was a bit annoying to have to set up my watch face data again but at least it’s done now. I just hope Garmin will eventually address their app for others who fall into this needless problem. Not sure why the Hiking activity can’t be added. Thanks again.