This particular error in speech is called a "Spoonerism":
In other words, it's generally a problem with reading and writing, and not with speech.
I think Spoonerisms have gotten associated in people's minds with dyslexia because dyslexia is often described as the visual swapping of letters while reading. And, screening people for dyslexia often involves a test asking them to deliberately create spoonerisms:
Dyslexia wouldn't be suggested from someone demonstrating spoonerisms in speech, rather it would be suggested if a person were poor at creating them when required to.
Spoonerisms don't seem to be regarded as indicative of any pathology, that I can find: