If you are a senior developer you shouldn’t be spending any time on practice interview whiteboards. You should already know how to code with confidence and be ready to honestly disclose where your experience ends. A good senior developer provides solutions to problems, which is more than pressing buttons on a keyboard.
The problem a senior is more likely to encounter is navigating the stylistic code biases of a controlling interviewer, such that if you aren’t writing code their way you are wrong. This is absurd. You either must have the confidence and soft skills to talk though those biases, if are adept enough to identify them, or be willing to work exactly their way like a beginner even after they hire you.
A huge red flag when interviewing are places that cannot differentiate junior developers from senior developers. For example if a junior developer is reliant on some tool for important basic requirements then a senior must be an expert at that tool completely ignoring the idea that such a tool is likely completely unnecessary.
Some people need interview prep. It could be that some candidates lack the soft skills. If the interview conversation capabilities don’t come naturally then you are projecting a false persona to be hired, a fraudulent first impression that evaporates once hired.
I do empathize with people trying to play up their capabilities just to be hired. There are tons of developers that are drastically under qualified for the seats they occupy.