That's not a very good argument, because then you could say the same for American, Canada, South Africa, Australia and so on. If recency is an issue, then here's a list of colonies that got their freedom around the same time:
Cyprus, Somalia, Sierra Leone, Kuwait, Tanzania, Jamaica, Trinidad and Tobago, Uganda, Kenya, Malawi, Zambia, Malta, Gambia, Guyana, Botswana, Lesotho, Barbados, Yemen, Mauritius, Eswatini (Swaziland).
If what you're saying is right then you'd have to admit Jamaican and Barbados English are just the same as Kenyan or Nigerian... but they're not. They're radically different because they're radically different regions. Uganda and Kenya being similar is what I would expect, but not necessarily Nigeria...
>They're radically different because they're radically different regions.
They're radically different predominantly at the street level and everyday usage, but the kind of professional English of journalists, academics and writers that the author of the article was surrounded by is very recognizable.
You can tell an American from an Australian on the beach but in a journal or article in a paper of record that's much more difficult. Higher ed English with its roots in a classical British education you can find all over the globe.
Cyprus, Somalia, Sierra Leone, Kuwait, Tanzania, Jamaica, Trinidad and Tobago, Uganda, Kenya, Malawi, Zambia, Malta, Gambia, Guyana, Botswana, Lesotho, Barbados, Yemen, Mauritius, Eswatini (Swaziland).
If what you're saying is right then you'd have to admit Jamaican and Barbados English are just the same as Kenyan or Nigerian... but they're not. They're radically different because they're radically different regions. Uganda and Kenya being similar is what I would expect, but not necessarily Nigeria...