Yes, and the channels through which information reaches someone inside are more numerous than most people on the outside realize.
Inmates receive letters, emails, and phone calls from multiple people. Anyone on the outside who knows both of you and has access to him through any of those channels can pass along information, true or embellished, without you ever knowing it happened. People who want to cause problems in a relationship have a direct line in through the same communication systems you use. It does not take much, one phone call to his mother, one letter from someone with an agenda, and a story lands in his ear with nobody to counter it.
With less than a week until release, the timing makes this particularly painful. He is days away from walking out and this is the moment he chooses to pull back based on something he heard through a third party rather than asking you directly.
What that tells you is something worth sitting with. A person who is willing to shut down communication days before release based on information he received secondhand, without a conversation with you first, is showing you how he handles conflict and doubt. That is relevant information about what the relationship looks like on the other side of the gate.
If the information he received is false, you deserve the chance to address it face-to-face. If it is true, that is a different conversation entirely.
Either way, the decision he makes in the next few days is his. What you do with however things land is yours.