The Flow Metadata Documenation lists the various run modes (
The context that the flow runs in. Valid values are:
DefaultMode — How the flow is launched determines whether the flow runs in user context
or in system context. In the UI, this value appears as User or System
Context—Depends on How Flow is Launched.
SystemModeWithSharing — The
flow respects org-wide default settings, role hierarchies, sharing
rules, manual sharing, teams, and territories. But the flow doesn’t
respect object permissions, field-level access, or other permissions
of the running user. In the UI, this value appears as System Context
with Sharing—Enforces Record-Level Access.
The doc seems to be missing the latest addition which is
However, going off the above and your specific scenario - the warning can be ignored. While it's technically true that the
runInMode is mismatched, how the flow is run in default mode determines the context and, in your example (record-triggered), that would be System Mode (as the other answer notes) which matches your subflow's context.
For other situations, this warning may be useful if the flow is being run in a different manner which would cause the resolved contexts to mismatch.