Surfaces are Removed when Unioned?

I am currently trying my best to not use materials while'st building in order to avoid material lag. However, I have come across an issue. When two parts with surfaces such as studs or inlet are placed side by side, it can come to look rather unpleasant.

Here is an example of this: https://imgur.com/a/2ZBajja

Now normally the answer to this problem would be to just union the two parts, but this is where the issue mentioned in the title comes in to play. The surfaces end up being removed when I union the two parts.

Here is what the parts look like when not unioned: https://imgur.com/a/til4r8Q

Then when I union them: https://imgur.com/a/N7lT6Vw

I have tried shifting through the properties of a part and have found no luck finding any property that will fix this, I also checked the dev wiki, where I still had no luck. Youtube and Reddit also did not offer me any standing towards this issue.