Sage vs. Magma on DLP
Indeed, this is a threshold issue, but the real threshold is $2^{32}$, not $2^{36}$ as documented. You can verify this with the following test:
SetVerbose(&quot;FFLog&quot;, 2);
repeat p := 2 * (2^32-5) * RandomPrime(10) + 1; until IsPrime(p);
Log(PrimitiveElement(GF(p)), PrimitiveElement(GF(p))^Random(p));
repeat p := 2 * (2^32+15) * RandomPrime(10) + 1; until IsPrime(p);
Log(PrimitiveElement(GF(p)), PrimitiveElement(GF(p))^Random(p));

Unfortunately there does not appear to be a way to call Pohlig-Hellman directly, or at least disable index calculus.