I still don’t get the point, since I don’t see a tax effect. If you do, the program would be a disaster 
Pattern around ex-dividend dates looks like this.
It’s illustrative and a personal observation based on one account. Maybe others care to share their observations?
| US | IE | JP | |
|---|---|---|---|
| gross dividends | 10’000 | 500 | - |
| PIL received | 10’000 | 500 | - |
| US withholding tax stated | 1’500 | - | - |
| thereof reclaimed | 1’500 | - | - |
| Interest received | 1.39 | 0.52 | - |
| Interest received whole year | 1.39 | 187.50 | - |
As said, the European ETF is lend in smaller numbers throughout the whole year, the rate between 1% and 1.5% (total, you get half).
Hence the interest received is higher, whereas the PIL are tiny. Borrowers seem to not mind or even avoid ex-dividend dates.
The US ETF borrowing is concentrated in large numbers on ex-dividend dates, the rate between 0.1% and 0.2%.
So the PIL are high, but the interest received tiny. The PIL are taxed and reclaimed like dividends via DA-1.
No borrowing on a JP ETF.
edit: fixed an error on the interest received