This is a sorta controversial subject.
The short answer is no - they are not true to type. But they might be very similar, or potentially even "better."
Much of the literature highly discourages planting of seedlings with the explanation that they are not true to type and furthermore are usually poor quality.
But others such as the late Jerry Lehman suggest that if the parents of the seed are high quality, the seedling is relatively likely to also be high quality. Several backyard growers can attest to this fact - i know some whose favorite trees are seedlings.
I think when literature discourages planting seedlings, the assumption is you are planting random/unknown seeds or wild seeds. In this case I agree that there good odds of getting mediocre to poor fruit.
I think there is a chance that some named varieties coudl have more dominant genetics and therefore be more likely to produce true to type. But i'm not sure if we know what varieties those are.
Of course the pollen parent would have a lot to do with how the seedling turns out.
Bottom line is I would try to plant only seeds where both parents are known to be superior. Even then, in every case there is at least moderate potential for the seedling to be different/lower quality.