Why heavy frigates still avoided ships of the line

Should exceptionally large frigates and razees be reclassified because they differed so much from ordinary frigates?

Generally no. Their exceptional power did not give them the structure, gun weight, or height needed to fight ships of the line, so their operational role remained that of a frigate.

The rating scheme is summarized as three decks for first and second rates, two for third and fourth rates, and one for fifth and sixth rates. Heavy frigates and razees are treated as too few to justify reorganizing that system around the exceptions. Constitution, President, and United States had considerable power for frigates, but their timbers, height, and gun weight were inadequate for an exchange with larger ships of the line. A fourth rate's place in the battle line therefore distinguished its role from that of a heavy frigate, despite comparisons of individual ships. American captains who avoided two-deck opponents were making a sound tactical choice in this assessment. The Battle of the Nile example is a frigate destroyed by a third rate's single broadside, illustrating the danger of the mismatch. Speed and agility instead favored commerce raiding and profitable fights against more suitable opponents.