Amazing -- and welcome to our Forum ~

Gravenstein’s are weird They’re the fastest growing apple tree I know, they're both ‘spur and tip-bearing,’ they’re ‘biennial bearers’ (will cycle between extremely heavy & light crops), they’re a ‘triploid’ (needing pollen from two other sources) ...and they bloom early. But not this early!

I’ve a massive Gravenstein tree and consider them a must-have variety. I wouldn’t worry about the winter blooming… though I’ve never noticed mine bloom ‘this late.’

I’d mainly consider pollinators for it. It would be great if you could devote a couple of it’s ..lesser limbs to a graft each of Yellow Transparent and, if you can find any scions, Summer Red. I’ve other trees, but the key is bloom-time. And as mentioned, Grav’s are early - so complementary pollinators must bloom at the same time, which the two mentioned do.