Is that bechamel that Gordon Ramsay is adding to the lasagna?
Gordon says "white sauce", which is a simpler term for bechamel-based sauces and is quite common when making lasagna.

Yet the stuff that gets stirred in the bowl looks somewhat "fluffier" than classic bechamel and when it's piped has a "raggedness" that plain bechamel doesn't have, but smoother that pure ricotta.

My conclusion: it's hard to say for certain, but to me it looks like a mixture of both.