It wouldn't matter because campaigning on independence was never going to help their vote. Scottish people that want independence are already voting for them, it's completely baked in. That position prevented them from being able to expand from that base which is what helped them in them in 2015 vs 2017.
There's little they would have lost by doing that because if it worked they could just negotiate the Independence referendum with labour later. If it failed then the Tory's were going to get their majority regardless. They weren't going to lose anything from that. I honestly believe it was a strategic mistake and unforced error.
They're still going to return a majority and they do it stating clearly voting for them is also pursuing a potential indyref2 if all goes tits up. What about the people from 2015 who would go "Oh, SNP aren't mentioning indyref2 now in 2019, we'll vote for them!".
Then the UK votes Tory majority, Brexit is full-steam ahead and the SNP come out with, "by the way, now that we couldn't help Jezza we're pursuing indyref2!". "OMG THE SNP DIDN'T CAMPAIGN ON INDYREF2 IN 2019, I AM OUTRAGED!".
Nah, being open and honest is best. I stand by what I said and repeat, it's up to Scottish people to follow the UK off a cliff if they refuse independence in a Boris lead Brexit Britain.
People want more honesty in politics, but now we're discussing "dishonest" campaigning if it meets your goals of trying to squeeze more votes.