Quite cynical way of thinking, especially when it comes to the subject of child poverty. The rhetoric for a long while has been that anyone voting against anything is a "faction" or a "protest" which is a quite ridiculous way of thinking.
As for the Manifesto and standing by it, the party whip has been used far too much as time has gone by, to the point where it can be seen as sometimes having actual MPs there is pointless, I would expect any MP that I voted for to question things if it didn't sit straight (child poverty is up there of course) and any amendment should be looked at, and if it is deemed to be beneficial for the area they represent vote for it, not just toe the line.
Too many of our MPs are career politicians seeing Westminster as a way to future gains, shoehorned in to constituencies where they have zero concept of what really goes on nor really care, its a mess, and its not getting better, we need to seriously look at the selection process for MPs.