The newly introduced cosmetic Pets in Diablo 4 count as a Minion for Necromancers, which can negatively impact some builds — but Blizzard is working towards a fix.
Wowhead Necromancer Writer and Diablo Content Creator Seroc Ifkre recently discovered this issue with Pets and posted a video on Youtube yesterday detailing these findings. The impact of this issue was also corroborated by Diablo Content Creator MacroBioBoi in a separate video.
Since the Pets count as a Minion, this will interact with Sacrificial, Stand Alone, and other effects that rely on having no Minions summoned. With these two specific effects respectively, players using the Sacrificial Glyph will deal less damage with a Pet active and those that use the Stand Alone Passive will instead lose 2% Damage Reduction for having the Pet active.
Fortunately, Blizzard is aware of the issue and will be putting out a fix for Pets in an upcoming Patch.
In the meantime, it's recommended that Minionless Necromancers take heed of this issue and either adjust their builds temporarily to accommodate the current bug, or temporarily dismiss their new furry friends — but don't worry, you'll be able to bring them back out soon.