Nobody fits OEM tyres to anything.
OEM is what was fitted at vehicle manufacture.
What we ALL fit is aftermarket replacement tyres which are approved by the tyre manufacturer for the vehicle we want to fit them to.
Avon do not recommend fitment of ST55/56 to the ST 1300.
They do recommend them for fitment to the ST1100.
Bridgestone, Dunlop, Pirelli/Metzeler all have recommended fitments.
It appears that tyre pressures for the US market can be VERY different to the UK or other markets.
Because someone somewhere has good/bad mileage/performance/handling etc. from a particular tyre does not mean that someone else somewhere else will have the same good/bad mileage/preformance/handling etc as you.
I wear out my tyres much faster than most people on this forum.
Why?
I live in a rural area in the west of Scotland and there are many more bends than straights.
I now run my front Avon St55 Storm at around 40lbs/psi to help it wear better and up to a point grip better.
This Avon has a different cross sectional profile to most other tyres, this results in a better turn in, but long term could result in a very poor turn in if ridden extensively on long flat straight roads causing squaring off. This squaring could result in a very abrupt transition from straight riding to leaning over.
In my type of usage, standard front tyre pressure will cause more rapid wear and a very severe uneven wear pattern on the shoulders of the tyre.
We are all different, we all ride differently in different areas of the world and even our own country/state/region.
Tyres are a VERY personal choice and everyone will get different mileage/wear/performance/handling/grip from whatever tyres they use.
At this moment in time and on at least two different models of bike that Honda produce(d) in the touring market (ST1100, Deauville), the Avon ST55/56 tyres are THE best tyre of choice regarding just about every area of use, at least in the UK.
Will they work for you, try them and find out.
With regard to headshake, there are common causes of this, poor fitting of tyre, bad wear pattern developing on tyre, bad pressure maintenance of tyre, head bearings (adjustment/wear/lubrication), disc warping, wheel assembly imbalance, tyre imbalance, road surface imperfection, rear wheel assembly/tyre imbalance or all, or combinations of one or more of the above.
The ST is also very sensitive, it seems, to bad tyre pressure maintenance, more so on certain brands of tyre than others.
A fault in tyre manufacture is far rarer, but is not unknown, more likely is a failure to handle and store the tyre properly in storage and shipping.
Sorry if this seems to have turned into a rant but I do get a bit frustrated when people cover the same ground over and over again and fail to realise that there are such a diverse range of possibilities for the cause of the problem at hand.
Ride safe, but ride.