Those odds aren’t valid because you’re assuming random fake numbers, when I reality they tend to chose similar numbers to yours. You’re more likely to think a local number may be valid so will answer.
If they fake the same area code, how many legitimate numbers might you talk to there? Make sure to include all doctors offices, schools, local government, and anyone you might do business with, along with their full set of possible numbers. Now you e got a much larger set of possible conflict out of a space three orders of magnitude smaller, and you’re up to X/10,000,000 chances of blocking a legit number
What if they spoof more locally than just area code, greatly reducing the number space? What if they chose a legit number from your local area, not just any possible, reducing the number space still more? What if you have kids, so multiply the number of possible conflicts. Now it’s likely to affect some people, possibly someone you know