Tax Cost Ratio VDADX vs. VIG

[anovice]

Why would the Tax Cost Ratio be lower on VDADX compared to VIG (next to Trailing Returns you might need to click on Month End)?


VDADX: www.morningstar.com/funds/xnas/vdadx/performance

VIG: www.morningstar.com/etfs/arcx/vig/performance

[roi2020]

According to M*, VIG had slightly higher pre-tax returns (2 bps -5 bps) versus VDADX for the trailing 1 Yr, 3 Yr, and 5 Yr periods.
However, VDADX after-tax returns were 15 bps - 18 bps greater for the same timeframes.
I can't explain this discrepancy.
Daniel Wiener (The Independent Adviser for Vanguard Investors) compared after-tax returns for Vanguard mutual funds
with their corresponding ETF shares a few years ago.
IIRC, after-tax returns were the same or varied at most only 2 bps when the funds' expense ratios were the same.