For the described technique, no. However, it would be easy enough for one request to have a different length hostname than the rest which contained a checksum,

For the described technique, no. However, it would be easy enough for one request to have a different length hostname than the rest which contained a checksum, and if then try different combinations of the rest until it matched the checksum, which it would only need to do if it were out of order. And if that happened, you could increase the time between requests, to compensate.