Joseph,
The mission of any system is elaborated by what it does, not by what its called.
For example if I call the school bus a Transatlantic Ghormophonic Extravoyager, its system function would remain to collect children from their homes and to deliver them to school.
What was the function of the BMP-1?
It was armed with a gun firing an anti-tank rocket, a guided anti-tank missile, and had a team of anti-tank rocket-propelled grenadiers as passengers. It also had a team of riflemen to provide support for the grenadiers and the anti-tank missile operator when dismounted. Given that most passengers of the BMP-1 and most of its weapons were to be used in either anti-tank role or to support anti-tank combat tasks, the BMP-1 was an anti-tank vehicle.
The BMP-1 replaced the BTR-50, which was also an anti-tank vehicle. It was unusually large, and seated 20 'infantrymen'...on Moscow parades. In the field it seated ten artillery crew, towed a 100mm anti-tank gun and the rest of the cargo space was occupied by ammunition.
25mm APFSDS-DU rounds could under certain circumstances penetrate some of the T-55 and T-72 armour.
The Bradley vehicle needs to find itself in a favourable orientation to the target first.
However, the M919 ammunition was approved for production in 1996, three years after the Cold War ended.
The chances that a small (~100g) penetrator rod of causing serious enough damage to destroy an MBT is small, but not to be discounted of course.
Greg