Hello AdityaEM,
Thank you for posting in Microsoft community.
After doing some research, I might have found why it is a little confusing here. According to Office 365 plan options - Service Descriptions and this article, Microsoft 365 Business plans (Business Basic, Business Standard and Business Premium) contains Exchange Online Plan 1 license. While according to Data loss prevention, in order to make use of DLP features, we must have at least one mailbox with an Exchange Online Plan 2 license configured. So in order to use the whole set of DLP features, it is recommended to use E3 license and above. While the service itself is available according to Overview of Microsoft 365 Business Premium and my observations on a Business Premium tenant as below: (this license alone is not included in E3, which might be the cause of the difference)

For these three subscriptions (Business Basic, Business Standard and Business Premium), only Business Standard & Business Premium (Marked “Yes” in Security & Compliance Center - Service Descriptions) could use DLP with an add-on license.
For Microsoft 365 Business Standard and Business Premium to use DLP, we have to purchase Office 365 data loss prevention add-on (add to Exchange Online Plan 1), as footer 7 in Security & Compliance Center availability for business and enterprise plans states.
To use DLP features, one user needs to be assigned with a E3 subscription. To use DLP for the whole organization, the users should having Exchange Online Plan 2 license.
Please feel free to let us know if you have any questions about this. In the meantime, I’ll consult more professional members to see if there is a clearer statement about this. Thank you for your patience and understanding.
Best regards,
Nerissa