nooooooooob teeth, if a shielder has even a modicum of awareness he will --easily-- have time to switch to his pitchfork before a cavalryman is upon him, in an open field strategus battle you can see them coming from miles away. Besides this, shieldiers spend vast amounts of their time not fighting, during this time they may as well have their pitchfork out (remember, it's free).
Lol, I have been a long poke polearm exclusively for like a 1000 hours now and I deem my battle awareness above average at least, but when you are fighting an enemy team and there is about 5-10 cavalry consistently harassing the clusterfuck, you do not see them coming all the time, even when you are focusing on watching for cav only.
Maybe you are talking about the way towards the fight or when waiting for the fight, but cav deaths in those situations encompass only a fraction of total amount of cav deaths in a strat battle. The bulk happens when people are fighting, which is when you want your shielders to push and fight infantry, not have them watching for cav with pitchforks. Sure cheap poke polearms are nice for walking towards a fight, but even a 1h can defend against cav if hes aware, so I don't think the weapon will help much in those situations, because most just get caught unaware. In the actual fight, where cav does their damage, having a pitchfork would be detrimental, slightly so due to the added weight, but more so because shielders might spend a lot of time doing what they are not best at, which is watching for cav.