No. Time between the launch of the Wii U and the launch of the Switch was 4 years, three months, and 13 days.
The time between the launch of the GBA and the launch of the DS was only 3 years, 3 months, and 3 days..
So if the Wii U and Switch should both be considered 8th gen, then GBA and DS should both be considered a single gen too. But that's ridiculous. GBA was it's own gen, and was very successful, despite becoming a last gen system in a little over 3 years.