@erik_squires +1
Clamping voltage increases with clamping current. It can be 250Vpeak (line to neutral) at 1mA, but it will more than double at few thousand of amperes. Surge current will be reduced by inductance of long power line, but not with close hit, House wiring inductive reactance in combination with secondary protector will reduce peak voltage a bit more (smaller voltage differential = lower surge current = lower clamping voltage) . Strong secondary protection will always be better, but there is no excuse for not using any.
Eric mentioned in linked article, that huge number of joules is not needed. If we assume huge 10kA surge current lasting 10us and 600V clamping voltage it will produce energy of 10kA x 600V x 10us = 60 joules. Event is likely longer than 10us, more like 100us, but main energy peak is within 10us. 100 joule protector ought to do any job. Even small, one outlet, Belkin absorber ($9 on Amazon) is listed at 885 joules total - 295 joules in each of 3 modes - much more than needed.
Why whole house surge protectors are not enough
TL;DR:
One measure of a surge protector is the clamping voltage. That is, at what voltage does the surge protector actually start to work. Whole house surge protectors are limited to no less than ~ 600 Volts (instantaneous) between a leg and neutral or ground. That’s up to 1,200V if symmetrical.
The best surge protecting strips and conditioners clamp below 200 Volts.
Please keep this in mind when deciding whether or not to use surge protectors at your PC, stereo, TV, etc. in addition to a whole house unit.
I wrote more about this here:
https://inatinear.blogspot.com/2021/09/time-for-new-surge-suppression.html
No manufacturer of whole house surge protection claims that their devices alone are enough for sensitive electronics when you check the fine print.