I was wondering if it was a policy to mask all mosquito front transparencies to disguise the fact that many bombs were dropped by guidance other than the bomb sight, like oboe for example.
I think it is most likely zealous censorship to obscure the bomb sight. Without knowing the source and time of the picture it is impossible to even conjecture why that one in particular was censored in this way.
I think the same aircraft, uncensored, is the subject of the 6th photo.
Cheers
Steve