No, it's just wrong to say they're completely different metrics. The Venn diagram between the economic activity measured by GNI (national income) and the economic activity measured by GDP is almost a circle.
US GDP in 2021 was $23 trillion. US GNI (national income) im 2021: was $23.3 trillion.
"monetary flows"
You're right, remittances and foreign aid are income but not GDP.