Bangladesh became independent in 1971 not 1972. And it was not formerly part of India, but was part of Pakistan. Makes me wonder what else is wrong in that chart.
It's not just independence, but international recognition. Croatia for example became independent in 1991, but got recognition from the UN, US, UK, Germany and Russia in 1992.
Bangladesh got recognition from the UK and several European countries in 1971 AFAIK. By December of 1971, even the armed conflict was over.
Actually, being off by one year isn't such a big deal. Most maps from the first half of 1971 would not show Bangladesh. But it lists Bangladesh as being previously of India before 1971. That is just wrong since it was part of Pakistan from 1947 to 1971.