Giganotosaurus, Polymorph, and Legendary Actions

[Forevaxp]

Recent MM printings now forbid this on page 11. From MM errata:

Legendary Creatures (p. 11). This section has been tightened
up to include the following new rules:
• The opening has a new second paragraph: “If a creature
assumes the form of a legendary creature, such as through a
spell, it doesn’t gain that form’s legendary actions, lair actions,
or regional effects.”
• The final sentence of the “Legendary Actions” section is now
two sentences: “It can forgo using them, and it can’t use them
while incapacitated or otherwise unable to take actions. If sur-
prised, it can’t use them until after its first turn in the combat.”
• The final sentence of the “Lair Actions” section is now three
sentences: “On initiative count 20 (losing all initiative ties), it
can use one of its lair action options. It can’t do so while inca-
pacitated or otherwise unable to take actions. If surprised, it
can’t use one until after its first turn in the combat.”

Thanks
That’s disappointing but also balanced