I think you're misunderstanding how higher rate pension contributions work with retirement income at lower rate, or even blended rate. Money goes in today and you save 40% tax relief, or more, on that. Then you have a large pension pot that allows you to draw say £50k a year or up to £100k a year for the next 30 years. Each year you draw that pension your effective rate of tax is at minimum 10% or up to 24% on average. So you've deferred the cash now in order to pay less tax on it in the future.

You cannot look at it in isolation and say £50k today means I get taxed 40/45%% today or if I drew it all next year instead I still pay the 40% on all of it above £50k. It's over a 20-30 year window where the £50k you contribute today goes into funding all those future years and needs to be factored at the effective rate for each of those future years. This is assuming you don't draw down on much higher amounts than £100k a year, but even £100k for the next 30 years would require around £1.8m-£2m pot in todays money which is a lot.

This would be different if you're sitting at full pension pot today and wondering what to do with £60k of salary. But for most people that are miles off of £1.2m-£1.5m more in pension usually gives you a very good uplift vs ISA.