[css-gaps-1] Should `rule-break` and `rule-outset` accept two values?

[cdoublev]

rule-break and rule-outset are currently defined as setting the corresponding column-rule-* and row-rule-* longhands to the same value.

While accepting values for both longhands does not seem significantly useful (one vs. two declarations):

• the shorthand must serialize to empty string when the longhands are not declared to the same value
• gap accept values for both column-gap and row-gap

So why not accepting two values?

[oSamDavis]

I think the intention behind this was not deviating from the other bi directional rule properties such as rule-color, rule-width and rule-style. These shorthands were designed to behave like the border shorthand as space in the property grammar was prioritized for varying gap decorations over different values in different directions.

cc: @kbabbitt