If I'm understanding what you mean right, no I don't think so.
If we have two companies, one makes a widget and the other buys it and adds a clock to then sell:
Cost of making the widget $5, sale price $10
Cost of adding a clock $10, sale price $40
As two companies, the first has a gross margin of $5 and the second $20. If the companies were to combine, they'd have costs of $15 and a sale price of $40 = gross margin of $25.
If we have two companies, one makes a widget and the other buys it and adds a clock to then sell:
Cost of making the widget $5, sale price $10
Cost of adding a clock $10, sale price $40
As two companies, the first has a gross margin of $5 and the second $20. If the companies were to combine, they'd have costs of $15 and a sale price of $40 = gross margin of $25.
I might not understand the term properly though, I based it on this https://www.investopedia.com/terms/g/grossmargin.asp