"one stipulation is 50% of shareholders need to approve". With...

"one stipulation is 50% of shareholders need to approve". With respect, what you wrote is wrong.

The stipulation is that more than 50% of shareholders who vote need to approve the resolution. If say only 30% of shareholders vote then more than half of those shareholders who vote have to approve the merger resolution. In that instance if 16% of all shareholders were to vote in favour of the merger than that would meet the so-called headcount test (because more than 50% of shareholders who bothered to vote were in favour of the merger). Sorry if I'm laying it on too thick but in the Allkem merger process I know these two tests caused heaps of confusion and stress.

Here is an excerpt from page 40 of Allkem's scheme of arrangement that explains how the tests work (my emphasis).

At the Scheme Meeting, Allkem Shareholders willbe asked to approve the Scheme by voting on theScheme Resolution. The Requisite Majorities ofAllkem Shareholders required to approve theScheme Resolution are:

• (headcount test) unless the Court orders otherwise,a majority in number(i.e. more than 50%) of AllkemShareholders present andvotingat the SchemeMeeting (either in person (including online), or byproxy, attorney or corporate representative); and
• (voting test) at least 75% of the total number ofvotes cast on the Scheme Resolution by AllkemShareholders (either in person (including online),or by proxy, attorney or corporate representative).

Voting on the Scheme Resolution will be conductedby way of a poll. Allkem Shareholders (who are presentin person (including online), or by proxy, attorney orcorporate representative) will have one vote for eachAllkem Share that they hold at the Voting EligibilityCut-Off Time (refer to the Important Dates sectionof this Scheme Booklet).