I have not tested the recipe with tinned pears, but would expect that they would be too wet to use. If you do want to try it out, I would suggest drying them off in paper towels to ensure they aren’t soaking wet with the juices from the can. They also may cook down further and go a bit mushy in the final crumble. If you have tried this out, do let me know how it goes in the comments. The above is what I would suggest doing if tinned pears is all you’ve got.