TBH returning to work after time off can be very daunting no matter how professional and competent you are at your job. It's quite easy for something well meaning to come across the the wrong way - especially when people are trying very hard not to put it across the wrong way.
Would you feel the same if the project was given to another woman? How would you feel if the clients demands meant that your time off (which I'm presuming you'd be spending with your child) was disrupted?
One of my team returned from maternity recently and trust me it was difficult - 10 months away from work made it impossible for me do to anything but ease her back in while she took back on board all of her clients, not because she's a woman, not because she's a mother and missing her child but purely because the period she was away was a considerable time and it takes time to adjust - this would be the same for a male or female employee who had been away for that amount of time.
Personally in this case I think the reasons given were valid but maybe the delivery of the news not executed well.