There's no correlation between mining and network congestion (where there are many unconfirmed transaction), whoever write that just throw some terminology as buzzword.
I wanted to rent a BTC mining node from a specific individual/company but I'm not sure if it's a scam or not.
On a side note, avoid business with an individual if it's not someone who you can trust. For business with a company, check the existence/reputation of the company & make sure to read the contract.