Look at how LinkedIn and Microsoft operate. The two companies have their own offices, salary tiers, office perks and lots more. Every department (including roles like marketing, recruiting, sales) is separate. Heck LinkedIn employees even use Slack rather than Microsoft Teams. It is the perfect example of independent company culture regardless of ownership.
What you said might be true for the majority of acquisitions at that scale, but it is by no means a strict rule.
What you said might be true for the majority of acquisitions at that scale, but it is by no means a strict rule.