Clarification of non-destructive updates

[DavidFrahm]

Checklist

• Issue number for this PR: Add clarifying info on non-destructive behavior for update() #1125
• Docs included?: Yes
• Test units included?: No
• In a clean directory, npm install, npm run build, and npm test run successfully? Yes

Description

Updating documentation regarding non-destructive behavior for update().

Code sample

[davideast]

Thanks @DavidFrahm!