How to Go about Generating Product/Channel Fit

What is more effective - focusing on 1-2 channels in depth or targeting multiple channels at the same time for higher chances of finding a channel that works?
This is a question that I had to answer in one of my leadership and growth workshops I gave this week.
Here my answer and thoughts:
1. If you are pre product/channel fit, you need to think broadly about what channels could theoretically work. Create a long-list.
2. Look at the long-list and make realistic assumptions around those channels through which you can acquire your key target customers. Disregard non-key target customers and channels to them.
3. Product/channel fit requires not only a working channel but also a scalable channel. Exclude channels that are not scalable (unless you just want to acquire a few customers to test your product).
4. Look at your short-list of potential channels and test all of them while prioritizing the most promising ones.
5. Remember that most startups do not get one channel to work! If you find one or two promising channels in terms of channels that seem to work in a scalable manner, double down on them.
Long answer short: Start broadly and then double down.
What do you think?
* picture by Ricardo Gomez Angel