I would like to express the reason why it suggests the clear background for the icons of third parties and why it would be the correct option regardless of my tastes.
when Sam is asked for an icon for the ubuntu welcome
some members of the community designed a complete orange squircle with the circle of friends in the middle making the ubuntu logo go from being a circle to a squircle in its entirety, this violated the brand and in its search to make the icon without changing the identity of the ubuntu logo, Sam designed the following icon

if we look at the icon we identify the ubuntu logo in all its splendor, and we see the best solution for a third-party icon or brand in the suru style, this was an upstream decision and a very well designed design guideline where the icon or logo works like a pictogram on a clear vanilla squircle and it’s a wise choice from Sam
I can use the icon I want in my installation or I can create any icon that I want, but my comment goes in an objective and impartial way, expressing from my point what would be the best way to follow and it would be the clear vanilla squircle that was introduced in upstream
in the ubuntu welcome icon