Obviously I'm talking about the situation where "Chelsea holds talks with Lukaku". Sure, they can speak with his agent, but the agent cannot say to Inter anything else the club's have explicitly given consent.
The clubs communicate this before any formal engagement takes place. A lot of the transfer saga is informal, true, but when the reports are for intended bids (probably false, but since they caught the smoke, why not the fire as well?) it probably is a more advanced situation. You usually do not see a reported transfer bid unless there's consent from both sides. Or if it's all hogwash
What you're describing is the case with Lautaro Martinez and Barcelona. Which also escalated to the clubs exchanging communication at one point.
You're not wrong obviously, but we're simply talking about different stages of the same process.