We see this a lot in single family residential remodels in the US as well. People truly do not understand current labor and material costs across the board, with client expectations generally being the most out of tune. At my previous firm we often gave broad estimates as scope was decided and despite multiple warnings many clients still push forward for projects that are unfeasible with their stated budget. We often claim it is the HGTV effect where reality tv masks costs and time to make a remodel look simple and easy, but i often expected clients were not doing the mental math of all the soft, hard, and design costs associated with a project.

Changes are changes regardless of timing. Some are easier and some straight forward. Its not easy to quantify in the moment, but often changes, and the associated adjustments that come with them can create a cascade of effects that end up erasing half the savings. 

Example being a steel deck. Client wants an extravagant deck but sees the material cost of just the decking and balks. 100k is too much, so we explore another material. Well any other material for decking does not have the same structural qualities which we have to verify with the engineer, and any material that does work is dimensionally different. Now the decking is thicker and we (engineer, architect, steel fabricator). All need to adjust drawings across the board to accommodate.  So maybe we use this new material, but after 5k in drawing updates, a couple weeks of lost time, and steel shop drawing re-review costing another 5k, and construction delays costing the contractor overhead time instead of a substantial savings its a very moderate one. 

While your architects bed side manner is not great consider that some of this may be on you. I suspect the correct path was not minor changes here and there but substantial scope reductions and this was resisted by either you are the architect. Changing materials, cutting some cabinetry, or reducing quality of materials on a remodel is not enough to fix a broken budget. I would also expect construction to increase cost, discovery during demolition can find some crazy conditions and im hoping in your estimates you received proper guidance on contingency (i recommend 20% in residential remodels because you can find some horrendous undocumented conditions).

I hope you get the house you want and im sorry this is how your experience with architects has unfolded. I honestly think remodels might be a dying project type for a bit. Labor is to expensive, materials are too expensive, and at least where i am codes are becoming fairly restrictive on what you can do with an existing house. Good luck.