So if you disagree and you know it has no chance of succeeding in changing anything, you don't try and block the debate. You simply treat it as an irrelevancy and don't turn up. Which is what has been done in this case. Only enough no votes turned up to require a recorded vote, rather than just a voice vote (a lot of votes in the House of Commons are simply voice votes where the Speaker judges Aye or Nay by hear - any vote can be forced to a count but a lot aren't). If that hadn't happened, Labor could try and claim that they, say, got 300 votes instead of 274 and nobody could say for certain that they didn't. With a recorded vote, it's clear they didn't. If 300 conservatives had turned up to vote against it (which they would have if there had been any chance of the vote in favour getting that high) it would have looked like the government was panicking. They would have been panicking - because the vote wasn't that high.
To whom would it have seemed that “the government was panicking”? especially versus standing on principle?