It’s important to have some system to hold your feet in place on a recumbent trike. This is for safety, comfort, as well as for efficiency.
With your feet in front of you, you would need to balance your feet against the pedals, this causes you to waste energy. Also, if your feet slip off you can run your own leg over. This is not something you want to have happen.
There’s no downside to wearing these on a trike because unlike a two-wheeled bicycle, it’s not necessary to unclip when stopping. When you do want to unclip, twist your foot and the shoes will unclip.
There are several systems to accomplish this. Road bicycle systems have stiff soles and are not easy to walk in. Mountain bike shoes have soles with the cleats recessed into them, which can be walked on normally.
This is one of the reason ICE does not include pedals as standard equipment. You might already use, or choose to pick, a different system. ICE offers the same system we like and use personally. Shimano Pedaling Dynamics (SPD) mountain style. Shimano even offers this system on sandals. Pearl Izumi has several models that look and wear like gym shoes.
If your pedals are SPD, and that’s normally what we install on trikes we sell, then pick shoes that can accept two bolt SPD mountain cleats.