I am very sceptic on this - in my view - the British eye witnesses just describe what they usually did see - British infantry practice and not French one, here another example

Beamish [History of the King’s German Legion (London: Buckland and Brown, 1943)] on the other hand, picks up after this and provides some interesting details. After the account above he adds that Rittmeister Uslar-Gleichen reanimated the squadron as it was swept by a second volley, and “bringing up their right flank, appeared before the enemy’s bayonets on two sides of the square.” He continues:
“The two front ranks, kneeling, presented a double row of deadly steel, while those in rear of these, the steady muskets of four standing ranks were leveled at the devoted horsemen. At this critical moment, when sword was about to be matched against firelock, and the chivalrous horsemen against the firm foot soldier – when victory hung yet in equal scales – an accidental shot from the kneeling ranks, which killing a horse, caused it and the rider to fall upon the bayonets – gave the triumph to the dragoons!”

Now instead of one front rank kneeling and 3 ranks, the eye witness sees two front rank kneeling and 4 ranks.

So - 3 ranks against 4 rank, one rank kneeling versus two ranks kneeling, or maybe not even paying that close attention in the heat of battle??