In fact, the deleted scenes also include an alternate introduction for James Marsden’s character as well, so there was a lot more content earlier in the movie at one point than what we got.
The version of Sonic the Hedgehog we saw gets through the backstory stuff much faster.
Perhaps there was a feeling that the opening needed more action, or, more than likely, the feeling was this version of the scene just went on too long.
In the end, the change doesn’t impact the larger story.