Sentence A – using "always" with the present progressive to describe an habitual action – is an alternate way of saying sentence B.
Sometimes it's possible, and very expressive, to structure a sentence in the way that sentence A is structured to describe a recurring action of somebody. Often the speaker is complaining about the person s/he is describing.
Other examples like this:
"¢ I can't stand my roommate! He's always leaving dirty dishes in the sink.
"¢ Will you please let me finish my sentences? You're always interrupting me!
"¢ What? You forgot your keys again? You're always forgetting your keys! You should tie them around your neck with a string!
In each of the sentences above, you can, of course, also use the simple present tense, which would a statement of fact, not necessarily showing your attitude. In the sentences above, however, you are showing annoyance.
It's also possible to show extreme approval with this construction, although it is less frequently used in this way::
"¢ Oh, Mary is so generous! She's always giving money and her time to charity organizations.
"¢ Bob is a born handyman. He's always looking for something to fix in his house.