3 of the plants Evve shows are Portulacaria, which have the same growth habit as Crassula.

Is there any negative in issuing very shallow planters as opposed to taller ones with room for way more volume of soil? "Negative" is subjective in that the pot typically looks better, but shallow pots are more difficult to grow in because they typically have a much higher % of saturated soil after a thorough watering. This makes it essential to either choose plants very forgiving of being over-watered, or ensuring you're using a grow medium that holds so little excess water it makes it difficult to over-water. As you learn more about bonsai, you'll find practiced growers are very particular about their choice of grow medium, and alter the structure and components to suit individual plants.

Most grow media based on fine ingredients (peat, coir, compost, composted forest products) are not good choices for shallow pots because they hold excessive amounts of water. For example, if you use a medium that supports 3" of excess (perched) water at the pot's bottom, using that soil in a 3" deep pot would find you growing in a soil that is 100% saturated after a thorough watering. It would be challenging for even skilled growers to maintain a jade or mini-jade (portulacaria) healthy in a situation like that. Notice how pot depth affects the amount of well-aerated soil a pot can hold after a thorough watering:

The pots are completely filled with soil. The shaded area represents excess (perched) water.

Note - if you shift your focus to using the upright form of portulacaria for your bonsai endeavors (or other trees with naturally small leaves), you'll be able to produce a much better likeness of a tree you might find in nature. This is due to portulacaria's leaf size which is more proportionate to the scale of a smaller plant.

Al