Water (and money) under the sill?

After the AGM I had a discussion with an ex architect who lives in Ben Jonson House about sills on the sixth floor south side full height windows, how they were designed, how they'd actually been installed (and leaked) and how the leaks were fixed. He drew this diagram (to which I added some labels):

The evolution of the sills

The original Barbican plans specified sills with a notch in the bottom (1), but the sills were installed with no notch (2), so moisture could (and did) get under the sill and into properties causing (e.g.) carpets to rot.

At some point, possibly as part of the work on the roofs, mastic or some such material was injected beneath the sills to plug the gaps (3).  This seems to have worked but it's not what the original plans called for and may not work as well as the specified notch.

Are there any plans to review this fix?  Was the cost charged to residents and will it now be refunded as part of the roofs refund?  I shall ask the BEO.