LC... Wakefield was given city status in 1888, but that’s for Wakefield itself (population 99,000). The City of Wakefield is the metropolitan borough created in 1974 and covers completely unrelated towns to Wakefield. Birkenhead is almost exactly the same, the actual settlement of Birkenhead has a population of 88,000.
Being the biggest city not to have top flight status might not be a badge of honour, but being a bigger city in general is a source of municipal pride.
Plymouth as a city is bigger than Wakefield, Southend, Birkenhead and various other places that have given themselves an inflated figure by chucking in completely unrelated towns and vast areas of countryside and villages. Plymouth hasn’t done this, but if it did it would include places like Ivybridge, Saltash, Torpoint and Tavistock and take in closer to 400,000.
You said it yourself, you’re talking about urban areas and metropolitan boroughs rather than the places themselves. Suggesting Southend itself is bigger than Plymouth is plainly preposterous.