I am an Indian citizen planning to go to India via London or Frankfurt. I won't go outside of airport. I heard rumor that you need a transit visa due to changes in European policies. Is this true ? Does it make sense at all
Yes, Indian citizens usually need a transit visa even if you are going to stay airside, but if you have a valid US visa, you will not need a transit visa in most cases. It shouldn't be too hard to obtain, so don't despair.
There are some more exceptions for this rule which you may qualify for: