So a kid going post grad would then play summer ball at the 18U level before his post grad year? A quick scan of the Perfect Game site shows very few 18U events...can the kid play 17U to play with his new class?
Yes, the kid doing a PG year could play 17u PG events summer before the PG year, since for recruiting purposes he is then considered a 17u "class" recruit even though he is now an 18u technically, I believe.
But the benefits of this extra summer of exposure have limitations. For example, a kid who doesn't get the recruiting outcome he wanted and suddenly decides in May of his Sr. year of HS that he is going to do a PG year that next fall and get another summer of exposure? Waste of $, as coaches would have turned the page on him the previous summer when they last saw him. Seeing him out of the blue at a PG event a year later would not draw new or renewed attention, I don't believe. Unless he grew 3" and added 5mph to his FB. If they made a final judgement on the kid the previous summer they will not waste their time to take another look.
Most kids who "reclass" or take a PG year begin advising recruiting coaches of the action by their Jr. year of HS, so coaches can automatically begin looking at the kid not as his current grade year but at the year/class of his 5th year of HS whether as a PG or as a reclass kid (usually done by repeating HS Jr. year upon transfer from public to private school). That way they do keep the "page open" on a kid for that extra year before making a final decision, and are not caught off guard seeing him that extra summer.