There are more factors to look into than just PCI.
The boom Bangladesh experienced was heavily affected by its LDC status and its over-reliance in garment exports (that constitute 90% of its total exports). It doesn't have any manufacturing industry yet either.

The government has also been accused of deflating its population to increase its PCI.
Bureaucracy in the country is also notoriously lazy. It's also far more dense than India.

High female labour participation is followed by a drop in TFR in Western and East Asian nations, so it becomes problematic in the long run.
Without children to pay taxes, you won't have a social security net for your needs later.
Kolkata has a TFR lower than Berlin already.

Also, most of that contribution in Bangladesh comes from women working in sweatshops that pay measly.
This has resulted in Dhaka ballooning into a metro and taking a Kolkata/Bangkok like development trajectory.

*hard manufacturing