No, they did test their Meltdown code on AMD and ARM but were not able to reproduce it on the chips they tested on.
That does not prove that a Meltdown-like attack on AMD or ARM is impossible, either on a different chip they did not test on or with a tweaked version of Meltdown.
From the actual article ("meltdown.pdf"):
We also tried to reproduce the Meltdown bug on several ARM and AMD CPUs. However, we did not manage to successfully leak kernel memory with the attack described in Section 5, neither on ARM nor on AMD. The reasons for this can be manifold. First of all, our implementation might simply be too slow and a more optimized version might succeed. For instance, a more shallow out-of-order execution pipeline could tip the race condition towards against the data leakage. Similarly, if the processor lacks certain features, e.g., no re-order buffer, our current implementation might not be able to leak data. However, for both ARM and AMD, the toy example as described in Section 3 works reliably, indicating that out-of-order execution generally occurs and instructions past illegal memory accesses are also performed.