Probably because its based on a time frame. If you have inf with these landings then they have established a landing. Maybe both sides suck at hitting.
I like where attacking art and tanks get no 1st round attacks and attacking ships bombardment hit art and or a motorized unit first. If non then a inf.
Also when there is a landing most Inf won’t be on the beachhead. They’ll be dug in further back.
This rule is part of the Axis & Allies Global 1940 2E, House Rules Expansion
For The Allies to be able - to some degree - to replace the severe losses of ships and transports during the early stages of the War, Landing Crafts are a plausible solution.
Though limited in numbers they still pose a serious threat for example to Axis-occupied Europe.
Landing Crafts are cheap, high value transportation means.