From Wikipedia, the author of that article - Devdutt_Pattanaik is an Indian author known for fictional work and interpretations of ancient Indian scriptures
Someone with a scientific bent of mind would not 'believe at first sight' that there are only ten. They would ask 'Are there 10 verses..' instead of 'What are the 10 verses..'
Any case, the list of ...
I am not sure what he means by saying that "there are only two verses for the Sudras". There are many more such verses which either contain instructions for a Sudra or are related to them in some way. Here are three of them for example:
2.24. Let twice-born men seek to dwell in those (above-mentioned countries); but a Sudra, distressed for subsistence, ...
Manu Smriti 3.12. For the first marriage of twice-born men (wives)
of equal caste are recommended; but for those who through desire
proceed (to marry again) the following females, (chosen) according to
the (direct) order (of the castes), are most approved.
Manu Smriti 3.13. It is declared that a Sudra woman alone (can be) the
wife of a Sudra, ...
Yes, Vaishya is mentioned in all the 4 Vedas, because the Purusha Sukta has the word in it. And, the Purusha Sukta is found in all the 4 Vedas.
BrAhmano asya mukham Asit BAhu rAjanyah krtah Uru tad asya yad
vaishyah PAdbhyAm shudro ajAyata ||
His key part (or mouth) was the man of the word (BrAhmana). Into the
Prince (rAjanya), (referring ...
This is what the chapter 113 of Markandeya Purana says in this regard
A brahman who marries wives among all the castes, provided that
he marries first a brahman woman, incurs no injury in his brahman-hood.
Likewise a kshatriya who marries first a kshatriya’s daughter, incurs no harm if he marries wives from lower castes.
Thus a vaisya, who ...
The closest one can be found in Mahabharata, There was one Vaisya warrior who fought for Dharma and Pandavas against Kauravas, he was son of Dhritarashtra, his name was Yuyutsu.
Quoting from Sambhava Parva, SECTION CXV
And during the time when Gandhari was in a state of advanced pregnancy, there was a maid servant of the Vaisya class who used to attend on ...
Pattanaik appears to be quoting from Patrick Olivelle's translation of Manusmṛti but does not quote him fully.
Olivelle first presents an overall schematic of the Manu in the introduction to his translation, then goes on to argue that in the Rules of Action in Normal Times, only 10 verses are allocated exclusively to vaiśyas and śūdras.
We can then view ...