For established profitable software companies there was a cliff edge in 2022 when this change kicked in. Staff costs for previous years had already been fully expensed while only 20% of the current year's costs could be deducted.
Second, any sudden increase in research expenditures is now discouraged. This could make companies less nimble.
For unprofitable startups it could cause issues during a phase of very high revenue growth. They could suddenly be liable to pay corporation tax in spite of the fact that they are not profitable in any reasonable sense of the word. It would smooth out later, but that may be too late for some.
What I do not believe for a second is that this is causing major job losses. Companies like Microsoft or Meta do not reduce research or software development just because there is a temporary tax hit. It could be an extra incentive for an efficiency drive I guess.