Yes, to make sure both is in the same level. The reason for adapters is because some guys will want to have a certain barb for a uniform look and often, they come in G1/4" only. Even if overall, they look almost the same, there is still a small ID variancy between brands.

The Thermochill is G3/8" so in the past, a good pair of barbs is almost non-existent beside TC ones till recently when EK made them. I bought my set last fall and for the 3/8" ID tubing, there is no barbs available for G3/8" period !