Exactly - interpreted code is harder to do timing attacks against because interpreters add a lot of timing "noise", while native code is much more consistent re: time taken to execute a specific routine.
a timing attack doesn't require constant duration for execution paths in the code. even with the noise in server communications remote timing attacks are often feasible - the noise filters out when you up the number of measurements or use the statistical techniques most modern side channel attacks rely on.
remote timing attacks contain noise by default, as they rely on server communications passed across a network with latency instead of examining the hardware directly to determine execution time. if you compare the network latency to the cache timing you'll find the noise is actually pretty fucking substantial.
a timing attack relies on a average difference in execution time between two paths of code. certain noise isn't going to protect you - for example, if everything on average takes 200ms longer, the average difference in execution time is still there.
I'm not saying timing attacks against interpreted code are impossible. I'm just saying they are easier to execute against native code, and thus have nothing to do with JS crypto being less secure than native crypto.
no serious person writes native code that vulnerable to timing attacks. if native crypto code has a measurable difference in execution time for different code paths that usually results in huge security advisories, patches, and it's against openssl a published paper. if the native code is written with constant time taken for all execution paths then by definition a timing attack is not possible. even if they are very close in execution time the timing attack is much more difficult, if not impossible.
timing attacks are only easier against native code written by people who don't know what they're doing, which means they made different execution paths take variable amounts of time, didn't examine the generated assembly by a hardware expert, and didn't bother to mask the crypto operations with proper noise generated using a cryptographically secure prng.
