The first gen Switch uses a 20nm chip, the revision (red box) uses the Mariko chip which is a 16nm chip. The OLED Switch uses the same Mariko chip.
Typically, most company increases the clockspeed of their chip if they are manufactured with a lower nm process – this made the chip runs faster. Nintendo chose to have parity with the first gen, so by keeping the same clockspeed the new revision model runs cooler and therefore gained extra battery life.
It’s up to Nintendo, they can easily change the clockspeed, allowing the Mariko chip to run faster at the expense of battery life. Maybe they will unlocked the clockspeed in future firmware? This will encourage OG Switch owner to upgrade.
Article From: NintendoLife.com