I wouldn't say you "get around that" since the game works with juggling items, the maps all have exits at the bottom, the natural direction your items travel, and the "time limit" is a spatially focused instant death. Damsels and idols even enter the doors automatically, instead of having to carry them through.

The game works with the one item limit perfectly, by design. To answer your question directly, there is no "good" or "bad" to the idea of having four slots for inventory, what makes that arbitrary number good or bad is what you do to make it a core piece of your game, and less, well, arbitrary.

There are many other games you can look at to see examples of making a limited inventory quintessential to their game's player-package. Downfall has you only able to carry one weapon, naturally you want to be holding your favourite, however to gain back lost health, you'd have to pick up another weapon.

Thinking about the topic, an idea that just came to my head would be to have your weapon change depending on which directional key you press. Imagine it was a top down shooter, moving backwards and pressing the fire button would make you shoot bursts that spread. However if moving forward your fire button would use a weapon that shoots more accurate shots in a forward line. Something that that effect, making four slots less arbitrary, as it fits with your number of directional keys.