Per WebIDL § 3.7.7, static operations use the same "define the operations" algorithm as regular operations:

To define the operations operations of interface or namespace definition on target, given realm realm, run the following steps:

1. For each operation op of operations:
   1. If op is not exposed in realm, then continue.
   2. Let method be the result of creating an operation function given op, definition, and realm.
   3. Let modifiable be false if op is unforgeable and true otherwise.
   4. Let desc be the PropertyDescriptor{[[Value]]: method, [[Writable]]: modifiable, [[Enumerable]]: true, [[Configurable]]: modifiable}.
   5. Let id be op's identifier.
   6. Perform ! DefinePropertyOrThrow(target, id, desc).

The [[Enumerable]]: true in step 4 applies to both regular and static operations. JavaScript static class methods are non-enumerable by default, so we need to explicitly set enumerable: true on SubtleCrypto.supports to match the spec just like we do with all other prototype methods.