Decompression question

Former US Navy Submarine sailor here with current AOW cert. Back in Basic Enlisted Submarine school (1980's), we did some training where they put us into a compression tank and increased the pressure to check if we would have any issues using the escape trunk on a submarine. We also performed a rapid ascent using the steinkey hood where we were trained to continuously say "Ho Ho Ho" on the ascent. I may have already answered my question, but I was wondering why decompression was not a consideration. We were told we could safely ascend from 300 feet from a damaged submarine. Buy the way, the escape trunks were more of a comfort to mom then us. We would not even submerge in water that shallow. I think decompression was not a worry because the submarine was never pressurized above 1 atmosphere and we created our own oxygen and removed the excess CO2 with CO2 scrubbers.