That is not true. I use a solar filter for my telescope and I can clearly see the Sun magnified.
This is the one case where it is true. I haven't checked, but it is possible that Betelgeuse is, too. All others are much too distant / small from our point of view.
The explanation is simply that objects that are much smaller than 1 degree in size, and are still less than 1 degree when magnified, won't look bigger. It's possible some stars exceed this size, but there are few, or you need a very strong telescope.
My point was only that Betelgeuse might be close enough and big enough to be more than a 1D point from our Earthly outlook since our eyes can just about tell that it isn't perfectly round even without a telescope. The Sun certainly is. No other star is.