iPhone

Source does speak about it more. It’s a question of not only how much work is being done, but what’s the difference of wages for the same work:

Despite contributing 90–91% of the total labour that goes into global production and the production of traded goods in 2021, including the majority of high-skilled labour, the global South received less than half (44%) of global income, and Southern workers received only 21% of global income in that year. In other words, while global production is overwhelmingly performed in the global South, the yields are disproportionately captured in the global North, indicating a disproportionate command of the global product.

labour exchange:

In 2021, the global North imported 906 billion hours of embodied labour from the South while exporting only 80 billion hours in return (a ratio of 11:1). On average across the period, the North imported 15x more labour from the South than it exported in return. In other words, the North net-appropriates large quantities of labour from the South.

and labour’s share of GDP:

We find that, globally, labour received, on average, 51.6% of world GDP during the 5-year period 2017–2021. In other words, only half of all value produced in the world economy (that is represented in prices and included in GDP accounts) is captured by workers in the form of wages... Southern workers’ share of Southern GDP is notably lower than the global average, at an average of 47.5% during the 2017–2021 period, while Northern workers’ share of Northern GDP is higher, at an average of 54.7% during the same period.

You are correct. This source, and many others from first world "third worldists" ignore this basic fact.
The term "unequal exchange" is misused by people. To say that profits come from unequal exchange is proudhonist, not marxist.
And this research paper assumes that all labor is of equal intensity.
Both are incorrect. This paper means nothing.

Labor in the third world of all skill levels produces less value per hour because of the lack of development of the means of production. Third world labor of equal skill produces less value in a global marketplace per hour when compared to that same labor applied to means of production in the developed first world. This is why the main task of every socialist government is to rapidly increase the stock of means of production and implement labor saving advances. i.e. a rapid industrialization.