Actually, "Vanilla" would be more in line with Bryan's original recommendation of:
2 sets during the 15's
2 sets during the first week of 10's and 5's
1 set during second week of 10's and 5's
Then either post 5's or negs.
Doing the 1 for 15, 2 for 10, and 3 for 5's is already a little tweaking made to try to maintain constant reps throughout the cycle, not exactly part of the "plain old" HST.
This is only if it matters to you personally. What you should focus on is doing as many as you can without sacrificing your ability to train frequently (meaning avoiding overfatigue, failure training, injury). If that's 2 sets for you, go ahead. If it's 4 sets, then even if that may seem a lot for others, if that's honestly the most you can do without getting overfatigued, then that's what you should do.
Regards,
-JV