so those numbers are apparently the max climb performance at the time
yes, but for what IAS?
TOGA @ an IAS of, for example, 130kts will not give the same climb performance as TOGA @ the correct IAS for the actual TOW, say 160kts.
The aircraft in this ficticious example would have been 30 kts behind the drag curve and most of the added power would gone into overcoming the drag to keep airborne, rather than translate into rate of climb. All imho.