Pump for shower - has the plumber made a mistake?

[DropZoneOne]

We've had our bathroom refitted. Including a rainfall shower that needed a pump. Pump was installed last night but not plugged in, electrician needs to come to do that. In the meantime plumber leaves note to say we can plug it to an extension lead.

We do that this morning. Shower is amazing. DH then turns sink tap on to brush teeth and pump kicks in!

I wasn't expecting this at all. Is it normal?

[wheresmyphone]

Ours just does the showers, not the taps.

[RandomlyGenerated]

Ours just did the shower too.

[Pombliboo123]

DP is a plumber and I've just asked him...

How exact response was a snort followed By "he's fucked it up. It should only do the shower"