These polls aren't covered by the MSM like the Fox/CNN/ABC/Gallup/Monmouth polls. So yeah you can have someone from the campaign come on TV and say "well our internal polls show different", but those figures aren't added to prediction models and RCP polling averages. They are essentially anecdotes. And a campaign wouldn't need to run a oversampling poll when they could just lie without running any type of poll. Remember polling costs money, Trump has spent 1.8 million on polling so far this cycle, no need to spend money on a fake poll that provides no real benefit.
As kingfish pointed out, there is a reason campaigns oversample, and Trumps campaign manager Conway, who is a pollster, knows this.