Opponents of Unionist Unity invoke the Fermanagh and South Tyrone result to undermine the case but does it?
There were a number of other problems that can help explain what went wrong:
A 'Faux' Unity - The lateness of the decision (and resulting ad hoc nature of the campaign), the localised nature of the decision, the distinct unhappiness of sections of the UUP and Tories with the decision, the refusal to follow through in South Belfast undermined how genuine the initiative looked (especially by UCUNF.)
The Tory link - This did not prove popular with the Unionist electorate overall so taking the whip, while a necessary compromise to get a deal, could have made the candidacy less appealing.
Localised rumours - Sinn Fein successfully spread a number of rumours that demotivated sections of Unionists voters e.g. Connor was pro-abortion were common led some evangelicals to stay at home. TUV types already somewhat sceptical of Connor's more open and liberal approach had a handy excuse to stay at home or spoil their ballot and the numbers would seem to validate that.
As to the claim of galvanisation of nationalism it is only partially correct. The nationalists who voted did shift but the nationalist vote was down (810). So it did not provide an extra impetus for nationalists to turn out.
Also in terms of political tactics success, while preferable, does not negate the utility of doing something. If Sinn Fein were faced with a split Unionist ticket in FST then they would have had little to worry, posted in their campaign and got the seat. With a serious challenge they had to expend political resources to do so e.g. busing down activists. These activists could have been elsewhere targeting other seats but this initiative made them have to worry about their own backyard. It has also potentially increased the risk to their Assembly seat in South Belfast.
It also misrepresents what unity could be. What happened in FST is not the only way of implementing it. It need not be full-blown merger but co-operation and collaboration of different levels of intensity across Northern Ireland or at a more localised level e.g. Belfast.