Two Forms Of Atzeret

Parshat Pinchas (29:35) בַּיּוֹם֙ הַשְּׁמִינִ֔י עֲצֶ֖רֶת תִּהְיֶ֣ה לָכֶ֑ם כׇּל⁠־מְלֶ֥אכֶת עֲבֹדָ֖ה לֹ֥א תַעֲשֽׂוּ

Rashi - עצרת תהיה לכם – עצורים בעשיית מלאכה

Parshat Reah (16:8)  שֵׁ֥שֶׁת יָמִ֖ים תֹּאכַ֣ל מַצּ֑וֹת וּבַיּ֣וֹם הַשְּׁבִיעִ֗י עֲצֶ֙רֶת֙ לַי״י֣ אֱלֹקיך לֹ֥א תַעֲשֶׂ֖ה מְלָאכָֽה

Rashi - עצרת לה אלקיך -  עצור עצמך מן המלאכה

Presumably the intent of the Rashi is the same that Atzeret means to refrain from work, so why does he express it differently, in Pinchas, about Atzeret, he says you are restricted from working but in Reah, regarding Shevii Shel Pesach, he says keep yourself back from work?  

We have to look at the context of the parsha.  In Reah, the Torah is discussing them mitzvot of Pesach and says regarding Shevii that it doesn't have the mitzvah of korban or matzah but the only command for a person is not to do work, it is referring to the commandments on a person, עצור עצמך מן המלאכה.  It is a command on the gavra to refrain from doing work.  However, in Pinchas, the Torah is describing the kedusha of the day and the obligation of thee korbanot for the day.  Hence, Rashi explains the עצרת is a hagdarah in the day itself, the day has a kedusha which obligates one to be in a situation of being restricted from working  (Likutay Sichos volume 33 footnote 34.)