Hola Todd

Yes, you're right, we often "blend" words and for a learner it's sometimes difficult to differenciate one word from another because of this. In this case we have two vowels which are the same between two words: habría abierto, so, when we pronounce this it sounds as a single "a" as you said. 

This is something that a face to face teacher would explain in a more conventional class, and the same goes for the rhythm and general intonation of words. Unfortunately we can't replicate this in a digital platform but I have taken note of it to see if we could plan an informative article. 

Saludos cordiales