It's fantastic there is a gang of cheerleaders cheering OP on. Grand, indeed!
However, as someone who has seen every possible side of every possible fence, I suspect the issue is the conflicting work-patterns.
I also suspect the meeting with senior staff will be to look at this issue.
None of this would have been discussed during mat leave as employees would consider/claim this to be harassment. Not doing so, ends up where OP is with a meeting on her return, armed mostly with sketchy, entirely partisan, information from colleagues, and zero understanding of the issue/s at hand.
From experience, what happens is staff (aided and abetted by HR!) knit their own work pattern. No-one gives a flying fuck regarding the practicalities of this for the service/supervised staff/physical resources until something happens. When that something happens, like a relocation, it becomes apparent there are issues around the uncovered/overlapping hours.
Mostly, situations can be resolved when working with emotionally mature employees. Where employees are less emotionally mature, e.g. viewing matters 'through the very linear lens of solely their own perspective' then redeployment is very frequently the outcome.
Usually, where the service is critical to the organisation, the jsp with the most conventional work pattern will remain in post as it is easier to marry that with someone also on a conventional (opposite) work pattern.
I have seen/been party to redeploying staff lacking flexibility for the benefit of supervised staff/service provision.
If I were OP, I'd be asking myself these questions in advance of the meeting:
- where/what are the gaps for the staff/service on the days neither jsp is present?
- is there enough work for two on the days both jsps are present?
- do both jsps supervise both staff members or is it split so that each jsp supervises one staff member?
- what flexibility can you offer to avoid redeployment?
In relation to confidentiality etc., by all means argue about it if you wish. However, bear in mind senior staff have already considered this and, no matter how precious the confidentiality issues are for you personally, corporately they are not registering similar concern.
Also try to factor in what many other posters have shared regarding how equally (or even more) confidential areas operate. Social workers, for example, undertake all manner of difficult calls in an open plan environment where confidentiality is required/assumed.
Just to reiterate what so many other posters have said - going in 'all guns blazing' will be manna from heaven for those seniors, really. 😂