Scrap metal equivalence in recipes

I don’t really understand the reasoning behind being able to make a lump of steel out of whatever size scrap metal, or a chunk of steel out of rebar and scrap, but requiring me to butcher a bunch of chunks of steel into scrap metal to make sheets seems a bit unwieldy(It bothers me at least).

Look, these recipes are calling for a specific amount of metal, but when a lump is specifically asked for it should be possible to use the smaller grades as well.
[table]
[tr]
[td][/td]
[td]Scrap metal[/td]
[td]Chunk of steel[/td]
[td]lump of steel[/td]
[/tr]
[tr]
[td]Scrap metal[/td]
[td] 1[/td]
[td] 1/3[/td]
[td]1/12[/td]
[/tr]
[tr]
[td]chunk of steel [/td]
[td]3[/td]
[td]1][/td]
[td]4[/td]
[/tr]
[tr][td]lump of steel[/td]
[td]12[/td]
[td]3[/td]
[td]1[/td]
[/tr]
[/table]
The recipes requiring one kind or another should be amended to allow for interchangeability(or a requirement to produce more if you only have one variety available).

I’m not sure if this was a decision based on realism or not, but it seems like varying the amount of metal required (or the amount of product produced) would more realistic.

Most recipes allow using larger chunks. Some may lack that.

However that would result in recipes offering more expensive choices for no gain. You could make a metal sheet from a lump, but you wouldn’t gain any compensation, just lose the lump and gain a sheet.
I guess that’s why most recipes for smaller items offer only scrap and sometimes chunks.