Sales period : Until March 31, 2019

Hi!
I visited the original Japanese Rail Pass website and there is a notice saying the Sales period ends on March 31, 2019, and therefore a 7-day JRP can be used up to April 6:

"JAPAN RAIL PASS is sold at some sales offices in Japan until March 31, 2019. * Restricted to individuals who possess only a passport issued by a country other than Japan (purchases cannot be made by Japanese nationals living overseas). * The sale details after the above date will be announced later."

The same date is also included in the sales details - http://www.japanrailpass.net/file/jr_pass_release_en_190117.pdf

What exactly does that mean? Since I am planning to travel to Japan on April 10-20, I would like to be sure that if I order my pass, it would still be valid on these dates.