I'm so strongly against this bill, not just because it can be misused in the way op has suggested. It is a law that is dictating for motive rather than outcome.
Quoting from the gov website about it:
*In assessing the nature of the conduct, consideration is to be given (among other things) to the question whether it involves any of the following—
(a) words or behaviour of a sexual nature;
(b) violent or threatening words or behaviour;
(c) controlling or coercive words or behaviour;
(d) use of economic pressure;
(e) use of psychological or emotional pressure.*
We already have laws that protect people from abuses of these kinds, especially when directed towards children.
Once you start legislating for motive rather than outcome, you create unintended outcomes.
If a child is abused, it is horrific regardless of whether the motive is homophobia, or some other motive, such as frustration about the child's SEN needs or disability: sadly, abuse with this motivation is much more common than homophobic conversion.
On the other hand, there are lots of possible circumstances where this law could be misused. For example let's imagine a young teenager is being groomed by a much older, same-sex partner and the parents are trying to keep the partner from seeing the child; the partner accuses the parents of homophobic conversion and "psychological pressure".
There shouldn't be asymmetric laws protecting some children from abuse more than other children.