That should also be true for pike and shoot then, instead they got a slight advantage over standard pikemans. One should consider the "fear" factors by using these early pistols into account, sort of "Berzerk" positive modifier to counter the negative modifier, which against melee troops would have to be considered. The same couldn't be said when taking into account Horses or Elephants, or Camels, which has disappeared apparently, which could be fenced off just by the smoke and sparkles; except the Horse in question is not Belophonte.
There are a mass of tactical modifiers that could be added (or subtracted) from Units, but given that Civ doesn't really show tactics, having unfolded the battles into county-spanning sections of the map, I wouldn't hold my breath.
There was a big difference between a musket, even a slow-firing matchlock like the early Pike & Shot used, and any pistol. Among other things, most pistol balls were too light and too low a velocity to penetrate a cuirass - n fact, French cuirasses were 'proofed' by firing a pistol at them, so every one issued had a little dent in it to prove that it was good enough. Musket balls were about twice as heavy and had velocities a third greater, and could penetrate any cuirass at short range. That meant that trotting up to a pike and shot formation to fire your pistols at them was a losing proposition for the cavalry, and in fact while pistoliers did manage to break up infantry that couldn't shoot back, for 150 years after the Tercios and Squadrons (Swedish) and battalions (Dutch) pike and shot formations arrived on the battlefield, cavalry had a very poor record against infantry. It was only after 1740 when they started charging at a gallop or faster to use the shock effect of massed horsemen that they started running over the infantry again, and infantry starting forming Squares to fight them off instead of just standing in line and shooting them down at leisure.
Battle of Blenheim 1704 seems like there were five armies, with four main cavalry- early curassiers regiments, with the savoy involved... I guess the savoy were the one crushed

they were notorious as to have wet powder all along...
There were 4 armies at Blenhiem (or Blindheim, or 2nd Hochstadt as the Germans call it . . .): Marlborough's Army of "the Sea Powers" (Dutch and English and their hired 'allies'), Eugene's Army of the HRE, the French Army of the Rhine and Army of Germany under, respectively, Marshals Tallard and Marsin. Nobody knows exactly how large any of the armies were, because the battle took place in August and they had all been marching and fighting since May, but best estimates are about 115 - 120,000 men on the field, of which about 1/3 were cavalry or dragoons. Of the mounted troops, the only cuirassiers were the Bavarian and Austrian regiments and the Danish contingent of the English/Dutch army, and the Danes were the only ones who actually charged at more than a slow trot and didn't waste their time firing pistols. Most cavalry, in western Europe at least, by this time were not wearing the cuirass at all: it didn't really come back in style until the last half of the 18th century - and that, at least graphically, appears to be what the Civ VI unit depicts.
Which means that, yeah, we've got about a 200 year gap between the last 'knights' and the 'cuirassiers' as the game depicts them, but since the game races through those 200 years in about 30 turns, there's not really enough time to stuff another unit into the mix.