I had a thought as to why hearing aid smartphone app complications might not be available for Apple’s newer watch faces as pointed out by Narenkona in a post above.
While rambling on in another thread about Apple Watch complications (see the Edit_Update at the end of the linked post), I remarked that Apple warns users that complications have app background refresh on the Watch always on even if you think you’ve turned background refresh off in the general app Watch settings. Some always-on complications can cause watch battery drain. I seemed to have found that out the hard way for the Reminders watch complication where the iPhone copy of my Reminders app was linked to a pretty active Exchange Server account, causing the watch complication to frequently refresh and rapidly drain my watch battery.
Perhaps the reason that Apple or MFi HA OEMs have not made HA app complications available for newer Apple Watch faces is that HA app complications with background refresh might cause a significant watch battery drain. Perhaps Apple or the HA OEMs did not want to pull the rug out from under users by killing off HA app complications for the older watch faces that folks were used to using?
OTH, an Apple Shortcut complication to a HA app on the watch probably isn’t doing much until you touch the complication on the watch face to indirectly launch the HA app.