No shares would be sold before the closing date for the offer,...

No shares would be sold before the closing date for the offer, so small holders haven't missed out, however the minimum holding in shares was fixed, so if you didn't opt in to keep your position, your shares are now available to sell. If they are CHESS holdings, then they aren't lent out. If they are held under a custodial model, then they can be lent out. Read your terms and conditions that your broker sets out - it should disclose whether your shares are available for lending. If it doesn't say, then you can be fairly sure that they aren't. If that isn't enough for you, contact them and find out.

Note the ~11m shares issued after conversion by convertible holders. If I was to guess, I'd say BTIG was selling at least some of them for holders last week - there was one day where every single share traded was a sell. Just a guess of course.