Undervolting reduces power consumption at a given clock speed.
This keeps thermals in check and can enable higher core frequencies without excessive heat buildup.
Both YouTubers had similar results with the undervolted RX 9070 XT.

Der8auer then reduced the undervolting to 170mV, which resulted in a stable setup.
Alva Jonathan used the factory-overclocked ASRock RX 9070 Steel Legend for his tests.
Despite the significant performance boost from undervolting, it’s not all positive news for enthusiasts.
Overclocking the core clock, memory clock, and voltage of the RX 9070 XT remains a frustrating endeavor.
This limited overclocking headroom implies that the OC models are likely already operating near their architectural limits.
Now, if AMD can only ensure steady supply and curb the excessive markups by retailers.