Yes, I've seen it.

Typically, it happens when something causes the tree to defoliate in summer. Apple Scab or Cedar Apple Rust, normally.

Not going to hurt much, but it probably means the tree has very bad foliar fungal issues and will probably never look that great.

Some plants get out-of-sync and will bloom at odd times. I have an Azalea throwing a few blooms out now.

Since you just moved in, give everything a year or so to see what's what.

Linda

I had a summer drought stressed crab do the same when fall rains hit. The following spring it didn't leaf out, twas toast.
That said yes sporadic flowers like that aren't always bad.

I'm thinking that is Chaenomeles rather than a Crab Apple i.e. Flowering Quince. Flowers very early in Spring and often puts out blooms in the Autumn and Winter in mild periods.

I don't think so......see no spines and most in the trade here stay shrub height and aren't trained to tree form. I have an atrosanguinea crab.........similar flower. Not typical to see a few fall blooms, but not really rare either. We had bizarre weather last winter over large swaths of the U.S. I have lyonia shrub in full bloom now, it is NOT a fall bloomer.

I have a redbud with a few blooms on it right now. Just plants getting confused in the fall. It happens fairly often and it's usually NBD

I may well be wrong. But I would like to see better pictures of the flowers, leaves and the whole plant's habit.