Note that the names in the name manager has a scope at Workbook level, and NOT at the sheet level. Any named defined as such will be accessible (or readable) from any worksheet. And to your question of how the formula looks at names manager, even though it is not on the sheet, well, I guess that's the beauty of a name object in Excel (MS designed it to work that way).

By the way, you can actually use =SUM(LOOKUP(INDIRECT("rng"&B2),Vect,Rslt))>=13 since it is being used in a conditional format, and formulas used within conditional formats will work as an array formula based on how it is written.