I was also curious to look up this particular top gear episode which the Wikipedia is referring to - see Legacy section: https://en.wikipedia.org/wiki/Ferrari_365_GT4_2%2B2,_400_and_412#400GT
Jeremy Clarkson on Top Gear described it as "awful in every way".
I have seen this quote used a couple of time in articles. Clearly Top Gear and Jeremy Clarkson are prominent names and maybe are considered to be authorities by many. Obviously such comment from these sources does not work in favor of the 400. Just like the BBC Book you need to take the commentary with a pinch of salt. In fact it can be diminished since it's only a remark without any full explanation or justification.
The reference used on the Wikipedia page is pointing towards a YouTube video which no longer is present. I found the episode also on the official Top Gear website. I have now updated the Wikipedia page accordingly (cite-note 13):
Interestingly if you open this link it shows the 400 in the opening screen. The comment about the 400 starts at 2 minute 17 seconds
I wonder if this one is still around?