It’s certainly possible, only in so far that there’s nothing to stop you from putting in more, unless there are limits in place for the platform. And this doesn’t even account for people who contribute both to a cash ISA and a S&S ISA.
However, imagine if I had enough money to invest double, ie £40k into my ISA.
I then withdraw £20k by the end of the tax year, but my ISA will have benefitted from £40k’s worth of dividends, investment growth. I really can’t see HMRC thinking this would be ok to do otherwise everyone who could afford it wouuld be doing it!