For a lot of the basics (flour, sugar, rice, etc.) conversion formulas/tables exist, but I've found that if you use recipes from around the globe, it's much easier to just have measuring utensils for cups/spoons (US cooking volume units) alongside the standard metric volume measures and scales in your kitchen.

At least some of MFPs ("verified") raw ingredient don't seem to use those though. 100g of Avocados, for example, can easily have several thousands of kcal according to them.

A cup of pasta doesn't even compute, since the mass of the pasta will depend so much on the exact shape in question.

You can't substitute a cup of dried tagliatelle (huge "balls of yarn") for a cup of risoni (rice-sized grains of pasta) and be happy after eating that meal. :)

That's the beauty of 'user-generated content'. You can scan whatever you want, and if it's not in their system you can just put the details in yourself. That includes choosing what a portion is