It's true Tom. I've done a a lot of pike fishing year round and it is my own personal opinion that jan-feb is where you see the most pike with the tender mouth issue.
It can really effect the bite, In these months I like to make sure we have some soft dead bait hanging under the ice for them because they might not feel like chewing on a tough live sucker minnow.
Into later march I find more sharp toothed hungry pike than any other month of the year.
If you research it you will find all kinds of bold statements about it being true or not being true.
I don't know how to put a scientific spin on it but I can tell you I've seen it and I've come to understand that it is a real thing what ever the cause.
And because of it, early ice pike bite can be awesome, mid jan through feb can really slow down and later march is generally awesome again.
