According to the Agile Practice Guide, one of the principles of agile project management is to "build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done" (Section 2.1). This implies that the agile project manager should foster a collaborative and self- organizing team culture, where team members share their knowledge and skills with each other, and are able to adapt to changing situations. By asking the team member to work with their peers to knowledge share, the agile project manager can ensure that the team has the necessary information and expertise to continue working on the project, even when the specialized team member is unavailable. This is also consistent with the PMBOK Guide, which states that "the project manager should facilitate knowledge sharing among the project team and other stakeholders" (Section 4.4.3.3). References:
Agile Practice Guide, Section 2.1
PMBOK Guide, 6th Edition, Section 4.4.3.3