There's many different apple's so hard for me to guess. Here's a pic of the apple I used to get. I cut it exclusively for several years.
This is a decent size crabapple at a rental house. It's in the back yard, doesn't really bloom all that nice anymore and has just become overgrown. Thought about cutting it down several times but it's still healthy.
Any type of apple has a distinct aroma that I'm familiar with. I can't confirm by the pictures if it's apple or not but if you take just a small sliver of the wood and light it on fire, that should tell you by the smell.
For firewood purposes I would not make any significant distinction between apple and crab apple. They belong to the same Malus genus and readily cross-pollinate each other.