I can see one potential issue with counting down instead of up. The maximum number of hops a packet can traverse along the path is 255 because TTL is an 8-bit field. This means the program implemented that way would need to account for the worst case and start the tracing process with the TTL of 255. In turn, this leads to sending excessively more packets than required if the path ends up being shorter than that, which is often the case.
Aside from this, please correct me if I'm wrong, but it is my understanding that if a router along the path is configured to drop ICMP Echo Request packets, it will drop them in any case - whether we trace from the beginning or in reverse.