I know crating from the get-go is the popular strategy nowadays, but this is more my approach. I know all about the denning instincts and the safe space and all that, but honestly it's always felt a bit uncomfortable to me to just shut a scared puppy up in a crate. It's such a big change for them and so scary, and there's not much they can do to take their minds off of the stress of being alone and confined. Even with proper crate training, if you look at stressed out dogs, they often pace around and move a lot to sort of work it off, but they can't do that in a crate.
I'm definitely not opposed at all to crate training and use it myself to varying degrees with different dogs. I just also think a bit of flexibility like this can really help puppies adjust to being left alone.