I use two lenses – Tamron 75-250mm F / 3.8-4.5 Model 104A and AF-P DX NIKKOR 70-300mm.
When the lens is set to a focal length of 250 mm, the field of view of the Tamron lens is greater than that of Nikkor. The camera used was the Nikon D5200 with a sensor size of 23.5mm x 15.6mm.
It is commonly accepted that the focal length determines the field of view (similar discussion in this forum), but there is a case where the field of view is different depending on the lens models with the same focal length.
Here is an image of a scale / ruler with marks taken with both lenses at a distance of 3 m.
How can this be explained?