Hmm, you may be right.
My old
Raymarine ST6002 controller would tack through 100 degrees whether in wind mode or not. If I was in wind mode, then after autotacking through 100 degrees it would automatically start trimming to the wind.
Looking at the the P70 control docs, it appears that you do have to be in
wind vane mode to autotack. I can't find any description of autotacking without
wind vane mode.
However, I did just find an autoturn feature which looks like what I used to have. It will turn through a configurable number of degrees, either to port or to starboard. But, the manual says this is only available to
motor vessels. I don't know whether
motor vessel vs sailboat is determined by the
autopilot model or if it can be selected in the controller. If it can be configured, you could try setting it to motor vessel to see if this feature then works for you. I doubt it would be a viable solution, though, since there are likely other features and performance characteristics that likely depend on this setting.
I can see how a non-wind auto turn feature could have some risk on a sailboat, since you could erroneously hit auto turn in the wrong direction (downwind). Instead of limiting this feature to motor vessels they probably could have built in a confirmation feature, like pressing it twice to confirm that you really wanted to autotack or something like that. Even in a motor vessel there is some risk since there could be traffic.
I would never have thought to check for this feature in a new
autopilot controller, and I would have been sad to find that I couldn't autotack without a wind input.