How do you read a PFT with restrictive type spirometry but normal lung volumes?

Non-specific pattern. Initially, NEJM papers showed that these patients develop obstructive patterns in the long term but follow-up papers have shown that patients can stay in that pattern (non-specific) or develop restrictive or obstructive patterns.

The pattern is indeed non-specific and can be associated with a range of pulmonary disorders, including both obstructive (e.g. asthma, COPD) and restrictive disorders (e.g. ILD, neuromuscular disease). In some patients, no specific etiology for their abnormal lung function can be determined.