I'm fairly certain Albert Speer would disagree
He didn't. In fact, he was one of the principal sources of the bombing survey.
Overy explained it more concisely than I can:
From Overy, Richard, “Why the Allies Won,” W.W. Norton & Company, New York, 1995, isbn 0-393-03925-0, page 131:
The stifling of industrial potential caused by bombing is inherently difficult to quantify, but it was well beyond the 10 per cent suggested by the post-war bombing survey, particularly in the cluster of war industries specifically under attack. At the end of January 1945 Albert Speer and his ministerial colleagues met in Berlin to sum up what bombing had done to production schedules for 1944. They found that Germany had produced 35 per cent fewer tanks than planned, 31 per cent fewer aircraft and 42 per cent fewer lorries as a result of bombing. The denial of these huge resources to German forces in 1944 fatally weakened their response to bombing and invasion, and eased the path of Allied armies.
The indirect effects were more important still, for the bombing offensive forced the German economy to switch very large resources away from equipment for the fighting fronts, using them instead to combat the bombing threat. By 1944 one-third of all German artillery production consisted of anti-aircraft guns; the anti-aircraft effort absorbed 20 per cent of all ammunition produced, one-third of the output of the optical industry, and between half and two-thirds of the production of radar and signals equipment. As a result of this diversion, the German army and navy were desperately short of essential radar and communications equipment for other tasks. The bombing also ate into Germany’s scarce manpower: by 1944 an estimated two million Germans were engaged in anti-aircraft defence, in repairing shattered factories and in generally cleaning up the destruction. From the spring of that year frantic efforts were made to burrow underground, away from the bombing. Fantastic schemes were promoted which absorbed almost half of all industrial construction and close to half a million workers. Of course, if German efforts to combat the bombing had succeeded the effort would not have been wasted. As it was the defences and repair teams did enough to keep production going until the autumn of 1944, but not enough to prevent the rapid erosion of German economic power thereafter, and not enough to prevent the massive redirection of economic effort from 1943. Bombing forced Germany to divide the economy between too many competing claims, none of which could, in the end, be satisfied. In the air over Germany, or on the fronts in Russia and France, German forces lacked the weapons to finish the job. The combined effects of direct destruction and the diversion of resources denied German forces approximately half their battle-front weapons and equipment in 1944. It is difficult not to regard this margin as decisive.
At p 133:
There has always seemed something fundamentally implausible about the contention of bombing’s critics that dropping almost 2.5 million tons of bombs on tautly-stretched industrial systems and war-weary urban populations would not seriously weaken them. Germany and Japan had no special immunity. Japan’s military economy was devoured in the flames; her population desperately longed for escape from bombing. German forces lost half of the weapons needed at the front, millions of workers absented themselves from work, and the economy gradually creaked almost to a halt. Bombing turned the whole of Germany, in Speer’s words, into a “gigantic front.” It was a front the Allies were determined to win; it absorbed huge resources on both sides. It was a battlefield in which only the infantry were missing. The final victory of the bombers in 1944 was, Speer concluded, “the greatest lost battle on the German side…” For all the arguments over the morality or operational effectiveness of the bombing campaigns, the air offensive was one of the decisive elements in Allied victory.
