If the strainer fits your pot so that it works as a fry basket, then it's fine to use it as such. As long as:
- It'll sit flat in the pot so it doesn't spill all the potatoes out;
- The handle is long enough that you can pick it up without burning yourself on the oil;
- You're not concerned if the strainer gets burned-on oil which might make it less useful as a general-purpose strainer;
- The strainer is all-metal, which that strainer is.
If any of the above don't work, consider just dumping the fries in the pot and using the strainer to fish them out, but not leaving it in the boiling oil.