JTH...
I am not an honest 'Buy and Holder' - but, am normally relatively close...
Changing – increasing contributions or changing the allocation ratios of contributions - of current contributions does not negate a 'Buy and Hold' strategy. Increasing ones contributions during a crash can be thought of as being the essence of a Buy and Holder. You are increasing the value of DCAs. Reducing your DCA at an unsustainable market top when you have other bills to pay also does preclude being a Buy and Holder. And, changing contribution ratios means very little.
I would actually position that adjusting allocations in your holdings between a small number of allocation ratios - not exceeding a limiting swing (say 10% - 20%) - is not inconsistent with Buy and Hold. You are not really timing the market if you change current asset allocations a few points. You might not be a true invest and forget, but you are also not a trader.
Buy and Hold does not mean you cannot adjust, it means that you do not believe that a person can consistently pick a top and a bottom, and thus are unwilling to make massive allocation swings to current holdings. To me, swing trading huge ratios between safety and growth is the indicator of a Market Timing approach.