True, and the Bengal Army was larger than the other two Presidency Armies by a substantial amount, if I'm not mistaken. There was no single body known as the "Indian Army" prior to 1895.
The recruitment of Bengalis was limited due to them being labelled as a 'non-martial race' in the aftermath of 1857. This was primarily due to:
1. Want of soldierly loyalty (read unquestionable obedience) - they were viewed with a great deal of suspicion, but they weren't alone. The same happened with Hindus from central India.
2. Them growing softer as time went on (in terms of physical soldierly ability) - I shan't digress too much, but most of the fighting was happening on the frontier, and there were fewer chances of these soldiers seeing much action, especially through the later part of the 19th century. Again, they weren't alone; large parts of the Madras Army were disbanded, and few units remain, due to long periods of inactivity in the relatively tranquil south of India.
Had it not been for WWII, the martial races theory would have continued (and we wouldn't have the SSG today, mind you!).
The War opened doors for countless people as the British government tried desperately to boost recruitment for the war effort.
As a result of limited recruitment, prestige in the profession of arms amongst the Bengali populace fell (which, of course, had serious repercussions following independence). If we are to move to the era post independence, the Pakistan Army wasn't biased against the Bengalis in terms of recruitment and selection - it was simply the fact that soldiering didn't hold the same prestige for the people of Chittagong as it did for Chakwal. In fact, in terms of officer selection, Bengali candidates had higher rates of acceptance in the ISSB. Yet, they still croaked. This is something we see today as well - the Army is trying to boost recruitment of Baluchis and Sindis, by passing incentives such as relaxed standards (physical and educational) and extra marks due to belonging to an underdeveloped area in rural Baluchistan (or, indeed, Sind), so that propaganda peddlers with less than holy motives can be quietened to some degree. To this day, Sindis and Baluchis barely join up.
Ha! The same (non-existent) Army which forms an integral core of the Pakistan Army today.
If any imbecile wishes to label the Army as a Punjabi or Pathan Army, then there's a damned good reason for it. The reason in question being that, to this day, it is the Pathans and the Punjabis who join up in droves. It is not due to some inherent bias or prejudice on part of the Army.
And before anyone says anything, I have this on good authority with my two of my best friends (one from Dadu and the other from Mehar, both of whom happen to be sons of officers), and you'd be surprised at the stories they tell you about the perception of soldiering and joining the Army in interior Sind.