Light output will increase as input current increases, however only up to a certain point. As the current increases, heat generation will increase as well. The forward current is limited by the amount of heat that can be absorbed by the LED package without affecting performance (the amount of light emitted by the LED lamp diminishes as junction temperature rises).
Since light output is a function of forward current, it is limited by the heat sinking capabilities of the LED package. Through-hole lamps can dissipate more heat than chip LEDs thus resulting in a higher maximum forward current for the through-hole lamps.