If we can get a numeric out of the ComputedColumnSql string then we know it is a numeric constant. We can transfer that to DefaultValue in this case

src/EFCore.Jet/Migrations/JetMigrationsSqlGenerator.cs

@@ -717,10 +717,17 @@ namespace Microsoft.EntityFrameworkCore.Migrations
             Check.NotNull(builder, nameof(builder));
 
             if (operation.ComputedColumnSql != null)
+            {
+                if (decimal.TryParse(operation.ComputedColumnSql, out decimal result))
+                {
+                    operation.DefaultValue = result;
+                }
+                else
                 {
                     ComputedColumnDefinition(schema, table, name, operation, model, builder);
                     return;
                 }
+            }
 
             var columnType = GetColumnType(schema, table, name, operation, model);
             //int has no size - ignore