First of all the code in question causes compiler warning (with some compilers) when FREECIV_DEBUG is not defined - set of variables are only used in log_debug(), which expands to nothing without FREECIV_DEBUG, so otherwise those variables are "set but unused". This should be cleared also for optimization reasons, so that we don't calculate those unused stats.
Even if the log_debug() would show the stats, calculated ones are not per-player as one would assume from the player name and other player-specific ones. Those stats are zeroed only before iterating the players, not for each player, so they accumulate over players iterated.
First of all the code in question causes compiler warning (with some compilers) when FREECIV_DEBUG is not defined - set of variables are only used in log_debug(), which expands to nothing without FREECIV_DEBUG, so otherwise those variables are "set but unused". This should be cleared also for optimization reasons, so that we don't calculate those unused stats.
Even if the log_debug() would show the stats, calculated ones are not per-player as one would assume from the player name and other player-specific ones. Those stats are zeroed only before iterating the players, not for each player, so they accumulate over players iterated.