Is investing for the mid term (5-10 years) a thing?

Un couple demande conseil sur la manière d'investir une inheritance pour une période de 5-10 ans, avec une stratégie d'investissement à moyen terme proposée par un conseiller financier.

(UK) My wife and I (32) live in London and have been using the Bogle method since last year. We earn enough to cover our expenses, have some cash set aside for emergencies, and invest whatever is left in FTSE Global all cap. My wife will receive a large inheritance soon. While this is a blessing, it is also much more than we are used to handling. So we went to see a financial advisor to help us plan our allocations for this money (house, car, kids, and investments). While we will be doing the investing ourselves, the FA suggested that we have money for the short, medium, and long term. Essentially their advice was to keep anything we plan to use in the next 5 years in cash gaining interest, then 5-10 years in "low risk investments", and continue indexing for the 10+ year horizon. Is this "investing for 5-10 years" something we should consider? He showed us a portfolio (of course, actively managed) which included a small percentage of equities, some bonds, commodities, real estate, and a plethora of other things that I didn't know existed. I apologise if this is an obvious question, and my gut says this might be BS, but I wonder if there's some validity to this "mid term investing". If you read this far, thank you for your time :)