I don’t now about you, but it is like that for me. IRL I have a slight fear of heights, but in some of my dreams I can’t even walk out on a balcony without feeling sick. Yet, in some other dreams, I can fall out of a rollercoaster without feeling any fear. How about you? Are your phobias greater when dreaming?
Fears are more potent in dreams because you are experiencing your phobia directly, not reacting to external stimuli(Like seeing a dog in real life and thinking "Thats a big dog, I hope he doesn’t attack me.).
The dream relies on no outside stimuli, so your fears are already present in the object or person, and it requires no thought on your part! Thats why you might be immediately afraid of something instead of being afraid of it after thinking it could be dangerous.
Also, remember how in dreams you sometimes travel to some place only by thinking about it - I guess, if you’re afraid of heights, you might subcounciously be afraid that just by being afraid you will fall. That takes you into a vicious cycle that will heighten your phobia to far greater levels than IRL.
As Dazino wrote, a dog in the stret probably won’t attack you IRL, but in dreams, if you’re afraid and paying attention to him, chances increase that he will indeed attack, bark at you or do anything that gets you afraid.
Makes sense, I also meet bears often in my dreams, and often go “Oh, shoot, not again…”. The next thing that happens is me getting mauled by a bear 
I have phobias in dreams, but not in RL. I love hights and scyscrapers in RL, but in a dream, whenever I get on one I feel the whole building shake and I become extremely scared. HEY! Thats a good dreamsign! Anyway, also my dream fears have lately transferred into my RL life too, now I cant even think about getting on a tall building without being queasy.