Were the Corinthians in 1 Corinthians 4:8 actually spiritually rich?
No. The Corinthians were not yet spiritually rich like the Ephesians. Although 1 Corinthians 4:8 states they were full and rich, the context identifies them as still carnal, with a long way to go spiritually. They had not attained that maturity.
Les teaches that although 1 Corinthians 4:8 says "Now you are full. Now you are rich," the Corinthians were not actually spiritually rich in the sense of mature believers. He notes they were still carnal and not yet spiritually rich like the Ephesians; they still had a long ways to go. This connects to the surrounding argument that believers have what they have only by God's grace, so they cannot glory as though they had not received it. The discussion returns to the whole concept of salvation.
Now ye are full, now ye are rich, ye have reigned as kings without us: and I would to God ye did reign, that we also might reign with you.
More Questions
What did Paul mean when he told the Corinthians they were rich and reigned as kings?
Paul says the carnal Corinthian Christians were rich, full, and reigning as kings without the apostles, and the reason was what God had done in their lives.