They are and they aren't competing.
The problem is that "long experienced developers" are often worse than "unproven newcomers". They aren't any better and instead of being a "lob of clay", they are "molded steel" and all the bad habits will never go away.
True senior engineers from reputable companies are of course different than newcomers and they are interviewed quite differently at big companies. But the problem is that what candidates understand as "senior" and what FANNG companies understand as "senior", often have little to do with each other. And the reason is simply that most people who apply for a senior role, wouldn't even pass the entry level interview at a FANNG company. It's just the sad reality. And this does not mean the entry level interview is wrong. It just means that these "senior" candidates were instead just junior developers who never developed beyond that from a skill perspective (except in their own heads).
And at FANNG companies, to even be considered for a senior position interview, you MUST have the credentials on your CV to prove it. However, a lot of candidates will never be interviewed for a senior position, even if their CV is "ten pages" long, because its apparent that this experience will be unlikely to have prepared you for a senior position at a FANNG company.
Being a senior engineer at a FANNG company is demanding and difficult on many more levels than just raw coding. You could be the best coder in the world, but that won't make you a senior engineer. It will make you a top mid-level engineer and you will never get beyond that without acquiring non-technical skills. Most people simply won't be able to do this job, no matter how long they stay in the industry. And I can assure you that there is little similarity in how interviews are conducted for these positions vs. college grads.
A senior engineer is essentially a developer who wants to still code, while also being a manager and a leader.