I've been dumping all chemicals into the skimmer for I believe 7 seasons and no problems. Seals, O-rings, and other components should be made of materials that are resistant to pool chemicals. Solar covers are not. CarlD started another thread somewhere about his cover that bit the dust and I posted that one cover I had stated the warranty was void for chlorine levels over 1.5 ppm. I also asked how many pools run as low as 1.5. Without any great chemistry knowledge my guess is the combination of high chlorine levels, heat, and sunlight kill covers prematurely. When you pour in front of a return or around a perimeter there is no guarantee dilution will quickly occur. Pouring in the skimmer you are. Basically fresh water is sucked in, mixed with the added chemicals, then shot out the returns. Each person does what works best. If one is having problems that may be attributed to one technique, change techniques. If it ain't broke, don't fix it. However, many engineers will say, if it ain't broke, design it better anyhow. The skimmer works for me.
Al