This is 100% about flavor. Butter will give you this, EVOO will give you that, ...
Butter will give you a 'richer' taste, whatever that may mean for you.
Extra Virgin Olive Oil, generally speaking is far more powerful and may become overwhelming.
Any other oil will give you a different taste profile.
Sunflower oil may be the most neutral and therefor the most appropriate for Alfredo sauce. Cannola oil may be another neutral oil, but I've never used it myself.
Generally speaking, an oil is an oil is a fat (for emulsifying).
You've got to understand what the purpose of the ingredients is. In a crumble or streusel topping (my go-to in the category is an apple crisp), the (gluten/wheat) flour, butter, and sugar are actually all binders/structural components. Taste/flavor is part of it, but as in your experiments in the other answer, you really can't vary one element wildly (separate from the others) without significantly changing the results.
With that in mind, the butter in a crumble/streusel topping will affect the tenderness of the crumb (similar to cake/pastry). Tenderness will also be affected by whether you used cold, melted, or softened butter (or a non-butter shortening, like margarine or lard/Crisco). The tenderness goes to mouth-feel, which will affect how/when your tongue picks up on the diff flavors.
Similarly, the temp/state of the butter/shortening affects how & how much the sugar will dissolve/interact with it. Depending on what type of sugar you're using (granulated/white, dark/light brown, raw/demerara, liquid sweeteners like honey, corn syrup, molasses, or agave), cold/melted/soft butter will just have a different holding capacity for sugar, which cooks can take advantage of to "super-sweeten" or "under-sweeten" given fundamentally the same amount of sugar.
And of course in a crumble, your perception of the sweetness of the finished topping will be impacted by the filling, since there's (delicious!) flavor interaction during cooking.
So it comes down to ingredient preparation & choice and cooking techniques - not just raw proportions. Cooking is a sort of applied chemistry - sometimes how you put things together is as/more important than what you put together.
Best Answer
The secret lies in the folding of the dough...You may uses half the butter but you would ultimately have to fold it more before cooking it. The more you fold the dough the more puffy it gets, of course your results will get better with more butter, but in that particular situation, go with the extra folding, you'll get a decent pastry this way.