^FOLLOW-UP question:
1. if the user has a pool of shadow (which are invisible on the blockchain, yes?)
2. some of the pooled shadow are sent to a newly generated recipient stealth address,
3. when/if they are converted back to SDC by the recipient stealth address they would be completely anonymous?
"Competely anonymous" is not really a well defined term, especially when considering indirect inferences from timing factors and such.
Clearly the more you (and everyone else) use shadow (and using higher mix factors when you do) the less information you are leaking to potential blockchain analysis.
The scenario you describe is clearly better than frequent conversions back and forth, but not as good as everything being done with shadow exclusively. In order for that to happen every merchant, exchange, etc. needs to support it directly, and you also need to be willing to except the higher inherent costs of transactions.