What is the difference between a "Solution Architect" and a plain old "Architect"? (POA)

In my experience, a solution architect is someone who defines a solution that’s then thrown across multiple time zones for some poor offshore team to build, satisfying no one

I thought a solution ... is someone who is very bound to a product / tech stack. An AWS solution architect, for example, would not recommend you do on-prem or another cloud - their solution is always bound to AWS.

Exactly that. SA as I've encountered it is a vendor role, working on a technical level, collaborating with sales and other account folks, to identify how the vendor's products help the customer to solve their problems and to implement them.