Beech’s proposal was not for box-stock AT-6s. It was for a new AT-6 variant that does not yet exist.
Correction to my last post. It wasn’t for a box stock T-6. It’s the AT-6 that doesn’t exist in production form yet.
“We don’t know those risk ratings, but the Beechcraft company just emerged from bankruptcy, and the AT-6 aircraft is still in prototype: While Beechcraft has built thousands of T-6 trainers for the US and its allies, the specific variant on offer — the armed ground-attack version, the AT-6 — is significantly different and not entirely proven.”
So, again - Embraer showed up with a proven plane they’ve been making and selling for years. Beechcraft showed up with some nice pictures and a promise instead of what the contract letters demanded - production aircraft.