That isn't correct, but it's an easy conclusion to draw.
What this means is that both parties must participate in a transaction. With Bitcoin, and hence with most blockchains, you can send to an address; that address can be a cold wallet, or could not exist at all, in which case your cybercoins are gone.
With MimbleWimble both parties must participate (interact) to form a transaction, but this can happen asynchronously.
In other words, both parties must be online, but not necessarily at the same time.
Without having a semantic debate, I think the point is that since there are no static addresses, parties cannot send money in a one-way transaction. Every transaction must have a handshake. Those two people could be in person, or online, but they don't need to be connected to the grin network until either wants to post the transaction.
> you can send to an address; that address can be a cold wallet, or could not exist at all
I don't think this is accurate since the other party must participate.
I think you probably missed the beginning of that sentence, which was contrasting e.g. Bitcoin with the MimbleWimble approach.
The difference between 'both parties must be online at the same time' (true of, say, a phone call) and 'both parties must participate, even if it's during different weeks' is a substantive difference, I only wished to indicate that MW requires the latter, not the former.
What this means is that both parties must participate in a transaction. With Bitcoin, and hence with most blockchains, you can send to an address; that address can be a cold wallet, or could not exist at all, in which case your cybercoins are gone.
With MimbleWimble both parties must participate (interact) to form a transaction, but this can happen asynchronously.
In other words, both parties must be online, but not necessarily at the same time.